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FAQs on Freshwater Substrates: Physical Properties (Size, Angularity...)

Related Articles: Freshwater Substrates, Nice bottoms; Choosing the right substrate for your aquarium by Neale Monks, Freshwater Deep Sand Beds Work by Deirdre Kylie, Setting up a Freshwater Aquarium, Tips for Beginners

Related FAQs: Freshwater Substrates 1, FW Substrates 2,
FAQs on: FW Substrate Selection, FW Substrate Chemical Properties, FW Substrate Amounts & Placement, FW Substrate Changing, Moving, Adding To, FW Substrate Cleaning, FW Substrate Issues, FW DSBs,

Sometimes the size, shape and sharpness of substrate is very important. Oh, and it should sink!

Gravel Color for FH; and FW period.    8/15/11
I read all of your blog posts on this page back to 2006 before writing you.
You are incredibly patient to answer the same questions over and over again, especially about tank size and hump growth. Folks, READ EVERYTHING BELOW BEFORE YOU ASK A QUESTION! My 3 questions are:
Would you kindly elaborate and clarify on gravel color? You recommend dark color gravel but virtually every other site I have researched is recommending the opposite. Most are claiming that dark gravel dulls FH coloring, whereas white or bright colors enhance FH color development. This is confusing for a FH newbie.
<Fish that can change colours will usually try to blend in with their surroundings, and Flowerhorns aren't any different. They may tweak their colours brighter when flirting or fighting, or else make their colours more muted when stressed, but on the whole, they try to remain as inconspicuous as possible to predators while maintaining sufficient colouration to communicate with their own kind. Precisely how this maps out under aquarium conditions will vary, and given Flowerhorns aren't a species but a hybrid, there's at least another complicating factor too. I freely admit not to have kept Flowerhorns personally, but I've kept plenty of Central American cichlids, and the basic rule with them is that a neutral substrate, e.g., plain gravel, generally works best. It's not the only factor of course, with genetics, stress, overhead lighting, and the availability of shade all being at least as important. I will make this general point though, that Central American cichlids on the whole aren't happy about bright light upwelling from beneath them, but conversely, if the tank is too dark, the fish will reduce their colouring somewhat, just as they do at night. So a black gravel might work better under very bright light, while plain beige or even white sand might be acceptable under more subdued lighting. There's a happy medium to be struck, and generally plain gravel under ordinary lighting hits that spot nicely. Given the low cost of gravel and sand, you may choose to experiment yourself, and find out what works best for your fish in terms of aesthetics. I do worry that a lot of the advice about enhancing Flowerhorn colouration is much the same as that to do with foods to boost nuchal hump development -- questionable at best, and at worst putting the welfare of the fish behind cosmetic values or superstition.
Putting aside colouration, Central American cichlids are universally happier under subdued lighting because that's precisely what they'd experience in the wild. So I tend to be biased in that direction...>
I have a new 8" FH in a 55 gallon tank that is currently undecorated. After 2 days he's settled, good behavior and eating well, I will decorate as soon as I clarify colors and options with you. Given the tank size and 8" fish a cave will consume a significant portion of swimming space. Is this really necessary or can you suggest an alternative setup for this tank size?
<A singleton might not need a cave, but it's worth adding for the sake of the fish, and a flowerpot will work just as well without using up as much space as a pile of rocks. I've taken to using terracotta pots in larger tanks, with some of the fancy Grecian and other types looking rather fun once they have a bit of algae on them. Alternatively, if scrubbed clean they work in more formal arrangements with lighter substrates and things like coloured lights and air bubblers that look out of place in natural-looking set-ups.>
I have a 10" Pleco that could help with cleaning the tank. I'd love to alternate him between this tank and the 72 gallon he's in. Is this possible or will he most likely be attacked by a FH?
<Plecs generally work well, but there are specimens that "go rogue" and latch onto slow-moving cichlids and cause serious harm as they graze on the mucous cichlids produce on their flanks. We've had one or two such reports here in the last year or so. So while, yes, I've kept Plecs (Pt. gibbiceps, to be precise) with Central Americans, that was in a 200 gallon system with plenty of space, and in a much smaller tank your own experiences may be different. In any even, Plecs have no value at all as tank cleaners thanks to the volume of mess they produce themselves. Nerite snails make far better algae eaters and are sufficiently armoured they might escape predation by these cichlids. Because they don't breed in freshwater, they don't become a pest either. Tylomelania might be worth trying as sand-sifting scavengers for the same reasons.>
Thank you for your answers.
<You're welcome, Neale.>

Gravel and Undergravel Filters, FW, Neale's go    2/1/11
Hello Crew,
I hope all I going well for you there. I have several questions, please.
I am fixing to make some modifications to my 75 gallon FW tank. First I am taking the sand bottom out and replacing it with gravel. I have used gravel before but this time decided to try the sand but all the detritus shows up too clearly on it.
<A turkey baster is good here. But also it's a reminder that your water circulation is probably not that good. If dirt accumulates on the sand, then you need more or better mechanical (i.e., silt-removing) filtration!>
The last time I used gravel It was recommended to me by a LFS to used 1 pound per gallon (75) so as to have a substantial surface for my "good" bacteria.
<For an undergravel filter the weight of the gravel isn't really that critical. Instead, concentrate on the depth. Assuming you use a medium-grade gravel, 8-10 cm/3-4 inches is correct.>
Right now I am relying on media in my power filter for that and have had no problem. Would it be OK for me to use less gravel so I won't have as much to clean?
<If you aren't using an undergravel filter, then you can have the gravel as thin a layer as you want. But if the undergravel filter is being used, you MUST have above 8 cm/3 inches for results to be worthwhile.>
Also, I have had tanks with and without under gravel filters and have read both pros and cons on their use. Please tell me what your feelings are about using them.
<Undergravels are great, and reverse-flow undergravels are superb because they "push" solid waste into the water where the canister filter can get it. But the chief drawbacks to undergravels are these: [A] You're limited to floating and epiphytic plants for the most part, because plants that are buried in the substrate rarely grow well. [B] You're limited in landscaping because the gravel MUST be more or less flat across the bottom of the tank, otherwise most of the water will go through the thinnest part of the gravel bed (water flows down the line of least resistance). [C] You can't have too many rocks or roots because anything below them is essentially dead so far as filtration goes. [D] You can't keep fish that dig too much otherwise the undergravel filter will be short-circuited. On the plus side, undergravels are quite easy to maintain except for cleaning under the gravel plate every 1-2 years; they are extremely efficient as biological filters; and they're very cheap to set up and run.>
Lastly, I want to get one of those in the tank background inserts that look like rock and fit against the back glass. Could you please recommend a particular brand that looks realistic as well as allowing for the intake tube on my power filter to hide behind it?
<They're all good, and once algae is grown on them a bit, they can look extremely realistic. Here in the UK, the Juwel brand is particularly popular. But there are some cautions. Firstly, you need to almost always cut them to size yourself unless they're pre-set for a particular aquarium model. Secondly, they need to be Siliconed in place at least 24 hours before you add water. Thirdly, Panaque spp. catfish (and perhaps some other big Loricariids) will scrape away the paint, revealing the epoxy or polystyrene behind the paint.>
Thank you for all you do. You are appreciated. James
<Thanks for the kind words. Cheers, Neale.>
Gravel and Undergravel Filters, ala RMF    2/1/11
Hello Crew,
I hope all I going well for you there. I have several questions, please.
I am fixing to make some modifications to my 75 gallon FW tank. First I am taking the sand bottom out and replacing it with gravel. I have used gravel before but this time decided to try the sand but all the detritus shows up too clearly on it. The last time I used gravel It was recommended to me by a LFS to used 1 pound per gallon (75) so as to have a substantial surface for my "good" bacteria.
<Mmm, yes... a couple/three inches... of depth... functionally, depending on grade et al. considerations. Read here:
and the linked files above...>
Right now I am relying on media in my power filter for that and have had no problem. Would it be OK for me to use less gravel so I won't have as much to clean?
<Mmmm, yes, to extents>
Also, I have had tanks with and without under gravel filters and have read both pros and cons on their use. Please tell me what your feelings are about using them.
<All posted... do learn to/use the search tool, indices... For here:
and the pertinent linked files above>
Lastly, I want to get one of those in the tank background inserts that look like rock and fit against the back glass. Could you please recommend a particular brand that looks realistic as well as allowing for the intake tube on my power filter to hide behind it?
<Oh! There are some really spiffy ones available (differentially) around the world. Rather than referring you to something you won't be able to secure, DO take a look on the major etailing petfish websites in the country you live in... U.S.: Dr.s Foster and Smith, Marine Depot... .coms>
Thank you for all you do. You are appreciated.
<Welcome. Bob Fenner>
Gravel and Undergravel Filters, Now James    2/1/11
Under Gravel Filtration / Artificial Background
Hello Crew, I hope all I going well for you there. I have several questions, please. I am fixing to make some modifications to my 75 gallon FW tank. First I am taking the sand bottom out and replacing it with gravel. I have used gravel before but this time decided to try the sand but all the detritus shows up too clearly on it. The last time I used gravel It was recommended to me by a LFS to used 1 pound per gallon (75) so
as to have a substantial surface for my "good" bacteria. Right now I am
relying on media in my power filter for that and have had no problem.
Would it be OK for me to use less gravel so I won't have as much to clean?
<The key to an under gravel filter is to keep the substrate even over the filter plates. Water takes the path of least resistance. It will go through the area with the least amount of substrate covering the plates. A pound per gallon has always been a standard for a very long time. If you plan on having fish that dig, like cichlids, then this filter may not be the best option.>
Also, I have had tanks with and without under gravel filters and have read both pros and cons on their use. Please tell me what your feelings are about using them.
< They were a very popular filter in the 60's and 70's, because they did indeed provide the biological filtration needed to break down toxic ammonia into nitrites and then nitrates. Then wet dry filters and BioWheel filters became popular and more efficient and the under gravels started to go away.
I keep cichlids so they tend to dig down to the filter plate making it useless.>
Lastly, I want to get one of those in the tank background inserts that look like rock and fit against the back glass. Could you please recommend a particular brand that looks realistic as well as allowing for the intake tube on my power filter to hide behind it?
< I have an artificial background on a 50 gallon tank It is both a blessing and a curse. They look beautiful. That is the plus side. Now the con. side.
Installation can be a nightmare. They will not fit an acrylic tank unless you do some modification to the top. You are limited on the size of a glass tank you can put them in. I found a heavy duty glass tank with no partition in the middle. Any bigger tank than a 50 gallon and you need to remove the center brace, install the background and then replace the center brace. They are usually made of a poly foam material that tends to float at first, so it needs to be anchored down. Once installed you see that it displaces from 1/4 to about 1/3 of the available aquarium space for fish. Now the 50 gallon is a 35 gallon tank. You can now place the heaters and the filters in the back but now you have another problem You need to pump the water from behind the background to the front of the background where the fish are. You can use a powerhead or a canister filter to do this. If the water doesn't flow around the sides or under the background you will need to cut some holes or slots to let the water get to the back of the background. You will then need to glue some screen over the holes to keep fish from getting behind the background. Now that it is all set up and running it will look great for awhile until it gets covered with algae. You will need some algae eating fish to get the algae under control. Razor blades and scrubbing pads may damage the background. Just get the background that you like the most.
Brands really don't matter as they are all the same. Hope this helps.>
Thank you for all you do. You are appreciated. James
< Thank you for you kind words.-Chuck>

Garnet Sand as Substrate
Garnet Sand In an Aquarium - 2/7/10

Hi, There's a location nearby where sand was laid down for a forest service
dirt access road long ago. In one section the sand is 80-90% garnet, and is a beautiful dark purple color. I've been considering using it in an aquarium, most likely as a top layer on Eco-Complete, but I haven't found any references online to people using it. I wouldn't take enough to compromise the road, and could even replace it with sand similar to what was used everywhere else.
Chemically it seems close enough to normal silica sand to not be too abrasive, and it feels smooth enough to not being a problem. Average particle size is three or four times larger than play sand. I was curious if you'd heard of anyone else using it, and if you could foresee any problems beyond the standard anaerobic bed/hydrogen sulfide and diatom bloom problems sand can have.
If I do end up using it the plan is to wash it like crazy with a bucket and hose to get rid of all the organics and small particles, then bake it to sterilize.
Thank you, and thank you for excellent help on a previous question.
Matt Williams
<Most gravels and sands sold for the construction trade have a pretty good durability index and are really hard. These usually don't break down with heavy traffic driving on them. I would recommend washing it in a bucket until the water runs clear. Fill a glass with half of the material and then fill the glass with distilled water. Measure the pH of the water in the glass to see if the material reacts with the gravel. If there is no change after a week I would say that it is good to go.-Chuck>

What the heck? --sand balls/hydrophobic sand? Happy New Year crew! 12/31/09
<And you Sara>
Sorry if it seems I must be asking more queries than answering them, but anyway...
I'm setting up a tank for my boyfriend's son and thought I'd use this sand I'd never used before. The brand is "Estes." Well, when I started rising it, I noticed that some of it was floating in balls. I thought this phenomenon might resolve itself if I put it in the tank.
But it just balled up even more! What's going on here? It almost looks like the sand is partially hydrophobic... could that be? (pics attached)
Sara M.
<I think so... but will likely "un-clump" in the next day or two. BobF>

Re: What the heck? --sand balls/hydrophobic sand?   1/1/10
It's better today... but still baffling. What would give aquarium sand this apparent subtle hydrophobic property? Is it from Mars? or sprayed with trimethylhyroxysilane? :-P
Sara M.
<I don't know what the composition of the Este's gravel products are, how they're processed, but have encountered this "stickiness" issue before.

Re: Fish flashing and having spasms (RMF, any better ideas?). FW substrate choices    11/3/09
<<I don't have any better ideas... You have done an admirable job of summing up possibilities, actions to consider. But do want to state that there are other "suitable" types of FW substrates other than silicates; and often Silica sands are too sharp for many (e.g. Corydoras) use. RMF>>
<Bob, you are quite right about sand, which was why I stressed "smooth" silica sand, which *is* safe with Corydoras, as opposed to "sharp" silica sand, which isn't. But the point is an important one, and worth restating.>
I note that Carib Sea do describe their sands as "burrower friendly" or "soft belly safe" on their web site; wish other manufacturers of aquarium-grade sands and gravels would do likewise. Cheers, Neale.>
<<I certainly agree! BobF>>

Re: FW Sand, part. Callichthyid sys.  4/27/09
In your last response to me you said something about using sand as a substrate for my aquarium, because the Corys love it and stuff. But I've read numerous places that sand is a pain to clean and you have to kind of move it around frequently.
<Garbage. In fact, the issue with sand is that it doesn't HIDE dirt, and so people imagine it's dirtier. It's like when people say white clothes get dirty faster. No, they get dirty just as fast as any other clothes, you just see it more quickly. What happens with sand is that fish faeces and other remains don't sink into the gravel. On a bed of sand, they sit on the top of the sand. If you have a good filter, this means it gets sucked up, but if it doesn't, it collects usually in one corner. To be honest, it's actually easier to keep a sandy aquarium clean because you can see the dirt and siphon it out easily. A turkey baster is a good tool for "spot cleaning" if you don't have time to do a water change. No, you don't need to stir the sand all the time. Your Corydoras will take care of that!
Melanoides snails are also great additions, behaving like earthworms and keeping the sand spotlessly clean. Plants also play a role, and besides doing extremely well in sand, if there's some nutrient rich aquarium soil underneath, their roots oxygenate the sand slightly as well. Do see here:
Instead of using sand, though, I read that quartz sand is a really good choice.
<Provided the sand is smooth (not sharp) and lime-free, use whatever sand you like. Silica (silver) sand is what I use because it's so cheap and easy to buy.>
I was wondering if you knew anything about it, like if it's too sharp for Corys and if live plants are able to be planted in it (with something like Fluorite or Eco Complete underneath, or something along those lines) Here is a site with some of the quartz sand that I like
<Looks far too sharp. And hideous. Bright white substrates will make your fish "turn down" their colours, so they'll all look washed out. Trust me on this: plain "smooth" silver sand from your garden centre is (extremely) cheap and effective, and once you have some plants growing above to create some shade, fish love the stuff. A 25 kilo bag (a bit over 50 lb) costs me about 3-4 UK pounds, around 5-6 US dollars. Using it seems a no-brainer to me. Just make sure you don't get "sharp" silver sand, the alternative stuff
sold in garden centres.>
Once again, thanks :)
<Cheers, Neale.>

3m colorquartz sand   10/19/08 Hi Crew, Hope things are going well for all of you. I have been doing some reading about people having good results using 3m colorquartz sand in their aquariums. The 2 grades mentioned are "S" grade and "T" grade. I heard that the "T" grade was more coarse which kept it more settled and less likely to have dead spots. <Most hobbyists have not the foggiest idea how substrates work. Dead spots are not a bad thing, and in fact can help "close" the nitrogen cycle by providing habitat for denitrifying bacteria. Do see here: http://www.wetwebmedia.com/fwsubwebindex/nicebottoms.htm > But I also read that the "T" was too coarse for bottom dwellers such as Corys. <Coarseness isn't the issue, sharpness is; only use "smooth" grades of sand with catfish and other burrowers. If the bag doesn't safe "safe for burrowing fish" then avoid. The sand should feel round to the touch, not jagged. CaribSea explicitly state that their Tahitian moon sand isn't safe for such fish, and I'd be checking with the manufacturer of any sand prior to use. I'll make the point that the BEST sand is plain vanilla "smooth" silica sand from your garden centre. Quartz sand comes in two flavours, "sharp" and "smooth", and if it doesn't say "smooth" on the bag, don't use it.> Please give me your thoughts on both grades of this sand. I will be using a 75 gallon freshwater with no live plants or UG filter and I definitely want to use Corys. I have never used sand before and am worried about it not staying on the bottom and getting into my filter intake. <Your fears are unwarranted. A 1-2 cm depth of sand will be completely safe and very clean. Dirt doesn't sink into the sand, and in my (substantial) experience this substrate is EASIER to clean than gravel.> Also, I want to use some Malaysian trumpet snails. How many would you recommend to start off with? <Hardly matters: they breed quickly, especially if overfed. I'd add a dozen. If you find the numbers are out of hand, cut back on the food and clean your tank properly! Also, you can add the predatory snail Clea helena that effectively controls Melanoides populations.> And if I have about 10 Corys how many of the sinking wafers do I use and do I wait until night time when I turn off the aquarium lights to feed them? <I have ten Corydoras paleatus in my community tank and they get a couple of Hikari algae wafers most (but not all) nights. Seems to work fine, and they're constantly breeding.> Thank you for all you do. Skipper <Thanks for the kind words. Cheers, Neale.>
Re: 3m colorquartz sand   10/19/08
I know a while back you mentioned to me that I would need some floating plants to help the fishes colors from fading out from the glare off the sand. I did not want to fool with live plants. Do you know of a company that makes very realistic artificial plants? <I think we're getting out of WWM FAQ territory here! You're asking me questions about taste and judgment, to which I don't have easy answers. Go visit your local aquarium shop, check out the plastic plants on sale. Most of the modern types are pretty good, especially once they have a bit of algae on them. Plastic plants look best used in quantity and where only one, at most two, "species" are used. They look (I feel) crummy where people buy a dozen different types and stick them all in the same tank. Cheers, Neale.>
Re: 3m colorquartz sand
OK, well let me ask you this. I just read an article about java moss being easy to grow in an aquarium. Do you agree? <I've never found it *that* easy to grow, no. If you want zero effort plants, here are my three easiest plants in the hobby: Anubias is number 1. These plants will put up with almost anything, and can thrive even under poor lighting conditions. Buy them ready attached to bogwood and arrange them as required. Number 2 is Cryptocoryne wendtii. You buy this in pots filled with rock wool. So long as you leave the plant in the pot and push it into the gravel, you can't go far wrong. Does well under any light. Give a pellet of fertiliser every month or so and you'll have happy plants that will gradually spread out across the tank. Number 3 is Java fern. Again, don't bother with loose plants, in my experience they often fall apart; instead buy "mother plant" specimens already attached to lava rock or bogwood. Just add water! Take care with both Anubias and Java fern never, EVER to bury them in the sand or gravel. They're "above the sand" plants, which of course means they couldn't care less about what sort of substrate you use. These three plants will give you the "tools" to decorate any tank. Arrange as required, and basically leave them to it. Bob Fenner would also want me to mention floating Indian Fern, a very adaptable species that's easy to look after. For whatever reason I haven't seen this plant in England for years. But the other three species mentioned are all extremely common. While a little more expensive than bunches of Vallisneria or whatever, because they're all virtually unkillable, they're better value. That said, Vallisneria usually does well in most tanks, it just needs fairly bright light to thrive, so tends to look unhappy in tanks with much less than, say, 2 watts per gallon. Cheers, Neale.>
Re: 3m colorquartz sand   10/19/08

Thank you for the suggestions. Do you have a recommendation for an easy plant that floats that can help my fish maintain their color when using silica sand?
<Re-read my last e-mail. Answered this already. Cheers, Neale.>

Oscar turning grey. 4/15/08 I have an Oscar cichlid. We were given the Oscar in a 3-gallon tank, and while I didn't measure him, he was obviously too big for that tank, so I got a new 20-gallon tank and put him in there. He has so much space now and was moving all around. He rapidly turned a bit grey and red from his original black and red. I was wondering if this is just because he's getting used to the change of environment? Or because I have white gravel instead of colored gravel? <Well yes, white gravel will often make cichlids "fade" their colours. Most fish DO NOT like substrates that are brightly coloured. Use plain gravel. It might not be to your taste, but it will suit your fish so much better. And, after all, it's the fish who has to live in the aquarium -- not you! Anyway, you can't keep an Oscar in a 20 gallon tank. No way, no how. Let's be crystal clear about this: Oscars are big fish that produce a lot of waste and are easily prone to diseases like Hole-in-the-Head when kept in unhealthy conditions. You absolutely MUST upgrade his aquarium to at least a 55 gallon system within the next few weeks. This is non-negotiable. If you don't have space for a 55 gallon tank, you don't have space for an Oscar too, and sooner or later this fish will be poisoned by its own waste and die a slow, painful death. There are some lovely dwarf cichlids better suited to tanks 20 gallons in size. Do please research them as sensible alternatives. Cheers, Neale.>

Black (Silica) Sand grain size? 01/21/2008 Hello crew member. <That would be me, Neale.> I hope you're having a good morning/afternoon/evening (which ever it is in your part of the world). <Hmm... just about lunchtime here in Blighty.> If I have overlooked the answer to this I am sorry and please feel free to direct me to the link as I am more then happy to research/read for myself. <OK.> I have read several times where it has been stated that black sand (I think specifically black silica sand) is good, not only for bringing out the colour of freshwater tropicals, but also for certain bottom dwelling fish such as Corydoras. <Absolutely. Sand (actually mud) is what Corydoras like best. They stick their heads right into it, and spew the stuff out of their gills, trapping organic materials in the process. My Corydoras spend the summers in a small pond filled with mud, and they love it! Almost all freshwater fish live in places where the substrate is dark. But in aquaria we often use light- or brightly-coloured gravel or sand. The fish try to adapt their colours to this, and effectively mute the colours so they are less obvious to predators. The result is that we rarely see freshwater fish in their full colouration. (At least, for wild-type fish; fancy varieties of things like Goldfish are different.) Use a dark substrate and the colours on most fishes, but especially cichlids and tetras, really come alive.> I am currently in the process of setting up a new 45G freshwater tank (when I say in the process of setting up I mean it is currently sitting on a stand in my living room, empty and bare of all things including lights, filters, heaters, substrate etc... whereupon I come home from work every day and stare at it trying to decide what I want to ultimately do with it). I have used gravel in all my previous freshwater tanks and I like the idea of trying something new. Recently black sand has peaked my interest (I think Neale might have mentioned it to someone in the past week or so in one of his answers to a question). <Black sand is indeed the best. It can be a bit pricey, so shop around for the best deal. Also, don't forget only the surface needs to be sand. The bottom layer can be fine gravel, and you separate the two with a "gravel tidy". Surprisingly enough, the sand behaves itself and stays at the top. Mostly, anyway!> Well it would seem that none of the aquarium shops here carry anything other then calcium carbonate sand, so as Neale suggested in his "Nice Bottoms: Choosing the right substrate for your aquarium" I went to some garden centres. I finally found one that stocks black silica sand. <Cool!> So here's my question (finally). What grain size is best? They carry 5mm, 3mm and 1mm grain size, and I have to say even the 1mm grain size seems pretty big to me. I had envisioned something quite a bit finer then what I have actually found. Is the 1mm grain size what I'm looking for in my quest for the illusive "black silica sand" or should I continue my search for something finer and if so how fine (e.g. 0.5mm). <It actually shouldn't matter much. Finer sand looks really nice, but depending on the fish you're keeping, it does have the downside of getting everywhere (e.g., inside the filter) if the fish move it about too much. Corydoras and tetras aren't a problem here, but things like Plecs and Clown Loaches would be. So if you're likely to keep robust fish, then a coarse grade of sand would be perfect. But as a default, I think the 1 mm sand is definitely worthwhile. Your catfish will thank you! You haven't lived until you've seen a Corydoras with its nose buried in the sand and it's little fins quivering with delight.> Thank you Amanda <Happy to help, Neale.>
Re: Black (Silica) Sand grain size? Attention Neale 1/23/08
Hi Neale, <Amanda,> Sorry to bother you again. Thank you for your last response, I amused myself for a while imagining my future Corydoras sticking their heads into my future sand and spewing the stuff out of their gills. My last correspondence is attached below so you can pretend that you remember your previous e-mail to me :) <Very good.> I can see this black sand thing is going to be a headache for me (in a good way, sort of, well for my husband at least, as it seems it will keep me busy with this tank for a while, which means I won't be wanting another one....for a while). <Heh!> This black silica 'sand' that I found, I am now not convinced is what you were talking about or even what I thought it was. I am now even debating if they should be calling it sand. I bought a small bag (didn't want to jump in all at once), took it home and opened it. I had read earlier that day (apparently black sand is all the rage at the moment here on WWM) that I wanted to make sure the sand wasn't sharp, which means if I feel it; it feels silky smooth...not scratchy. Well this is about the un-smoothest (I know it's not a real word) 'sand' I've ever felt. <Sounds as if this is "sharp sand", used in horticulture to improve drainage. Good for plants, not good for fish.> Secondly, I'm not convinced it's sand, and it's certainly not 1mm (would really like to know who was doing the grading for that and what they thought a mm is). It's all irregular looking, with sticky outie bits all over it and I'm sure I could poke my own eye out with it if I wasn't careful. Then there are the needle like bits I can honestly envision the needle like bits in the bag impaling a small fish. <Doesn't sound like what you want. Save it for the houseplants...> Now to me sand is the stuff you find on a beach or in a river bed, stuff that's fairly fine and gets stuck in uncomfortable places and drives you insane because the more you brush it to get it off the more places it spreads to. It's not some rough pokey outie weird stuff that you couldn't imagine a Corydoras burrowing through without impaling itself on or getting it caught in its gills and suffocating to death. Am I just being woefully ignorant of what type of 'sand' I am searching for? <You're correct: the sand suitable for use in an aquarium needs to be of the type called "smooth sand".> Should I be looking for beach type sand (imagine the beaches in Australia and the type of sand there) or is this sticky outie stuff "it". <Beach sand is normally a mix of silica sand and pulverised seashells; while it looks really good in aquaria, the problem is that it raises the carbonate hardness of the water, which in turn raises the pH. These two changes are not always acceptable. Corydoras and tetras, for example, prefer water that's on the acidic side and soft to moderately hard. So beach sand tends to be a better choice for fish that like hard water conditions, such as livebearers. Mbuna and brackish water fish. River sand is variable: some river sands are identical to beach sand in being a mix of silica and lime, but others are purely silica and work great in aquaria.> I just really don't want to get something that will make my Corydoras (when I finally get the tank set up and decide what specie to get) unhappy, or even potentially hurt them. <Correct. Which substrate you use has a huge impact on how an aquarium looks. Although one of the less expensive parts of the set-up, the differences in terms of aesthetics between different substrates are huge. If all else fails, plain smooth silica sand (sometimes marketed as silver sand) works fine, and it's what I use in my tanks. Yes, it is bright and very reflective, but if you tint the water with blackwater extract (or put peat granulate in the filter) this can be toned down a bit, and once the plants and algae have done their thing, it looks very nice. The fish don't really care about the colour of the sand; it's more how the fish look to our eyes.> I get frustrated at times as things that seem to be quite common in the States and the UK are just about impossible to find here in Australia (don't even get me started on how long it took me to source Selcon....and then the price....I hope my fish appreciate what I go through for them). <I'm sure the right sand is available (and cheap) in Australia. Silica sand (silver sand) is such a basic commodity that you'll eventually find it. It's used a lot in indoor and outdoor gardening. Some people have apparently also got this kind of sand as "play" sand. So garden centres are usually places to find it. Black aquarium sand is always more difficult to find and much more expensive, at least here in the UK, where the price is something like 5 or 10 times that of bulk silver sand. For what it's worth, there are some superb fishkeeping clubs in Australia, such as ANGFA, and they may be able to help you as well. I'm always incredibly jealous of my Australian fishkeeping friends because of the terrific stuff they get to keep. Your native fishes are amazing, and only very rarely sold in Europe.> Thank you. Amanda <Cheers, Neale.>

Freshwater silica sand/substrate question(s) 1/19/08 Mates, <Hello,> Thanks for the all the help in the past and, generally, for keeping this site active and (extremely) useful. <Cool.> I am setting up a 120g freshwater tank, to house rainbows, Congo tetras, various Plecos and a few Corys. <Hmm... be careful with the "various Plecs" idea -- not all of them play nicely together.> I've got them all in a 50g right now, with HOB AquaClear (way oversized for current application), silica sand substrate from home depot, healthy amount of Mopani wood and some lace rock. A few freshwater plants for decoration...java moss and water lettuce. Everyone is happy. No casualties at any time...been good for about 9 months now. Plecos have been much less nocturnal recently...to me, a good sign they are starting to feel comfortable in their current home. <Indeed.> On new tank (don't know if it matters, but I'll give it out anyways), planning on dual internal overflow boxes from glass-holes.com with 1.5" holes on both, sump below with filter sock for mechanical filtration, FBF for biological (don't want bio-balls/bio-bale...too much commotion and trying to avoid as much CO2 loss as I can...it will be moderately planted with primarily low input plants...FBF just seems like the best fit), return pump either an Eheim submersible or pan world external. 240w t-5 full spectrums. I am planning on keeping plants on Mopani driftwood (like Anubias, java moss, java fern) and in pots, probably not going to drop anything directly into the substrate. <My feeling here is CO2 is a waste with very slow growing plants like these. Their growth is slow enough the ambient CO2 in plain water will be adequate. As you probably know, CO2 is something you need to add to brightly-lit tanks because the fast-growing plants need the CO2 for photosynthesis to keep up with amount of light. Your selection of plants live in shade and don't like a lot of light (Anubias tends to get covered in algae). Java fern also seems to thrive in hard, even brackish, water and likely removes carbon from bicarbonate in the water anyway. Since CO2 is toxic to fish if not dosed carefully, I'd balance any benefits against the potential risks.> This tank will probably be converted to reef tank in a few years...trying to plan for that during freshwater set up, but treat the freshies appropriately now. (Any other suggestions/warnings on the set up are appreciated). <Above.> Anyhow, I realized this week how much substrate it was going to take to fill up the tank. It is about 8 square feet...at 3" deep, that's about 2 square feet of substrate. That is a ton (well, not literally). Probably in the neighborhood of 150lbs of sand. For river sand/cafe sand/beach sand, that is going to be around $160 at the local LFS. <Yikes!> Now, as mentioned above, I've used the #30 silica sand from home depot. it is just listed as industrial sand, but states on the back purity in excess of 99.?% silica sand. I've used in two tanks with Corys, Plecos, aquatic dwarf frogs, and never had any issues (no casualties, no evidence of barbel/gill/skin/scale damage of any kind), other than it takes for ever to rinse and about a week to clear up once it is in the tank. I read in the Neale Monks article (great name by the way - "Nice Bottoms") that you have to watch out for 'sharp' silica...I have no idea how to tell if it is sharp or not. Can you help me on this? <Sharp sand is a specific grade of sand used in horticulture at least for providing good drainage in potting compost mixes. It's also used in building work of various kinds. The grains are angular rather than rounded, and it feels sharp or scratchy to the touch. Smooth silica sand, the kind used in aquaria, has a lovely silky feel.> As well, there are two different grades - #20 and #30. I combed through the internet (got to love Google) but couldn't really find an explanation as to grades and granule sizes. From what I could gather, #20 granule is bigger than #30 granule. Is this right? <No idea. Provided the sand is smooth, the size of the grains couldn't matter less really. I suppose bigger sand grains would be better in some ways, since they're less likely to get swooshed about into the water column when fish swim by. (And big fish really do kick the stuff up into the tank!)> Obvious, I'd want to go with the largest granules I can get to minimize dangers of compacting/anaerobic decay/nasty gases. <This issue at least is largely irrelevant. Anaerobic decay is a bit of an exaggerated problem. If you're not planting anything, then you don't really need much sand anyway. In deep sand beds, any anaerobic decay mostly breaks down nitrate (a good thing, encouraged in marine tanks!) and any H2S produced reacts virtually at once with oxygen should it get into the water column and has little real impact on fish health. Go visit a pond and see how much anaerobic decay there is there... and yet the fish are fine.> Last, and off topic but something I've always wondered, would a protein skimmer provide any benefit to a freshwater set up? <Generally no. A standard skimmer requires a certain amount of salinity to work at all. Brackish systems at SG 1.010 seem to be about the minimum. If the salinity is too low, the bubbles don't stick together and you don't get the froth. There are freshwater skimmers, but they're rather different (and bigger) and used primarily for ponds. Besides, in a freshwater system, water changes are so cheap that you may as well use them for nitrate control. Few freshwater fish are particularly sensitive to nitrate, so provided you keep things below 20 mg/l, you're fine, even with Discus or Tanganyikans. By contrast, marine aquarists generally want to maintain much lower nitrate levels than that. Bottom line, there's no particular need for skimmers in freshwater tanks.> Thanks. Paul in San Diego. <Cheers, Neale.>

Coarse Sand VS. Course Sand 9/5/07 Hi there! I like that you are sticklers for proper grammar and spelling, but I would like to point out something that I have repeatedly run across the last few weeks as I am thoroughly researching before setting up a 92-gallon corner tank. Many times when I read about sand size, the mention is for "course" sand. This is not only in your articles (sorry Anthony and others), but also in several books and magazines. However, my understanding, esp. after verifying this in a dictionary, is that it should be "coarse" - or am I missing something new in aquarium technology? I thoroughly enjoy all the articles on your website, and am thoroughly impressed with the breadth and depth of everyone's knowledge...so I hope either I am wrong in this term or it will correct some incoming questions' spellings. Thanks tremendously, Kerstin DeRolf:-) < According to the United Soil Classification System Method ASTM D 2487 the correct spelling is "coarse". Soils are classified and sold based on the size of the individual particles and percentage of each. The local fish store buys coarse sand from the quarry and should call it the same when it is sold to aquarists.-Chuck>

Appropriate freshwater substrate recommendation? 7/26/05 Hi crew! I am interested in using a sugar-fine substrate for my new freshwater tank. What would you recommend for such an application? Most of the sugar-fine recommendations I read (at least around WetWebMedia) are for Southdown play sand (and I remember at least one zoomed reptile sand recommendation). But since this is soluble for its buffering capacity and tendency to increase pH (which I don't suppose I need for my Arowanas), I would much prefer something that is non-reactive, insoluble, and doesn't need maintenance in the ways of periodic replenishment. Are there any inexpensive substrate options out there for me? Any recommendations, or even further suggestions would be greatly appreciated! Thanks, Phil <There are some pretty fine "natural" gravels of various sorts available in different parts of the U.S., world... I would ask at your local fish stores re, the "sand and gravel" outlets (check your phone book "Yellow Pages" re), and test them for chemical activity. Bob Fenner>

Silica sand Hello, I am new to this site and I am sure you have already encountered this question before, but please bear with me.  I currently have a 75 gallon  with 3 small Frontosas, 3 clown loaches, 1 Synodontis catfish, and 1 Pleco. I had aquarium gravel in this tank but upon reading articles about these fish I found  out they prefer sand substrates.  Many sites have said that you can use  pool filter sand as a substrate and I bought some. <Mmm, pool filter sand? I don't agree... siliceous materials are bad to use on a few counts... they're too sharp (hard on your loaches), too slick/smooth and pack down due to their two-dimensional structure (bad for biological filtration), and do naught for alkaline buffering (unlike carbonaceous materials...)> After cleaning it really well stirring it with my hands, I noticed little cuts on them. <Bingo> Finding more  sites, I now read that silica is actually sharp and will injure my fish,  yet  you said at one time you used sandblasting sand.  Isn't silica the same thing? <Maybe in some localities, yes... but not in all> Is there a sand more suitable that isn't as costly  as what my LFS is charging? Thanks, Wanda <All sorts. Please read here: http://wetwebmedia.com/FWSubWebIndex/fwsubstrates.htm and check out your local rock and gravel, landscape suppliers. Bob Fenner>
Silica sand for FW systems? Hello, I am new to this site and I am sure you have already encountered this question before, but please bear with me.  I currently have a 75 gallon  with 3 small Frontosas, 3 clown loaches, 1 Synodontis catfish, and 1 Pleco. I had aquarium gravel in this tank but upon reading articles about these fish I found  out they prefer sand substrates.  Many sites have said that you can use  pool filter sand as a substrate and I bought some. After cleaning it really well   stirring it with my hands, I noticed little cuts on them.  Finding more  sites, I now read that silica is actually sharp and will injure my fish,  yet  you said at one time you used sandblasting sand.  Isn't  silica the same thing?  Is there a sand more suitable that isn't as costly  as what my LFS is charging? Thanks, < When you write to this site many of the questions are answered by different members of the Wet Web Media Crew.  I personally have never recommended silica sand or sand blasting sand for the exact reasons you have mentioned. Others may have but I doubt it. This sand is made from silicon dioxide (Glass). It is crushed so the individual particles are sharp and abrasive. You want a sand that is rounded and smooth.  Beach sand has been weathered over hundreds of years and most of the sharp edges have been worn away. Check at the local landscape supply yards for better materials. Take a magnifying glass to examine the individual grains and see if they are smooth and rounded and they all should be the same size. Particles of different sizes become easily clogged with fish waste.-Chuck> Wanda

Fluorite and Corydoras I am planning to start a 37 gallon tank with angelfish and Corydoras. I have the plants planted in fluorite. Is the fluorite okay for the Corydoras or will it hurt their barbells?  Marc <Hi, Marc - it's not so much their barbels I'd be worried about, but their soft, scaleless bellies....  Fluorite is pretty sharp stuff, and I think that is a good concern.  Would you consider covering the fluorite with a thin layer of smooth gravel?  If you get gravel of a slightly larger size, it should primarily stay on top of the fluorite, even when you siphon/vacuum.  Wishing you well,  -Sabrina>

Sand for FW stingrays? (10/19/03) Hi, <Hi! Ananda here tonight> I have had a hard time finding sand substrate for Fresh water stingrays. Right now it is bare bottomed. I know it has to be silica free sand. It also can't raise the Ph of my tank.  I called some companies that make play sand. They all have silica in the sand just not in a free dust form. I read about silver sand on a UK website but no one states has heard about it. What do you recommend. <Not silver sand. It's silvery due to mica, which could scratch the ray's stomach. You will probably need to look for sand from a specialist fish store. You might also check with some of the companies that package sand for aquarium use, and have your local shop order some for you (since the companies are unlikely to sell directly to hobbyists).> thanks, john <Sorry I couldn't be of more help! --Ananda>

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