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FAQs on Filtering Brackish Systems

Related Articles: Brackish Components, Brackish Water System Set-up

Related FAQs: Brackish Water Systems in General,


Filter for brackish aquarium    /RMF   5/19/15
Hello WWM crew. I have a 125 gallon brackish aquarium 1.012 sg and am using a couple of canister filters and just purchased a protein skimmer.
My question is, are canister filter nitrate factories?
<They can be; if not packed properly w/ filter media, cleaned regularly>
I see they are not preferred for salt water but are they ok for brackish water?
If so, I may choose to raise the salinity in the future, at what point would a canister not be a good choice?
<Changing spg slowly (a thousandths or so maximum per day) can be done w/ most all types of filtration. The issue is not changing it too much, too fast that it impugns biological filtration.>
Thanks for the help.
<Welcome. Bob Fenner>
Filter for brackish aquarium   /Neale        5/20/15

Hello WWM crew. I have a 125 gallon brackish aquarium 1.012 sg and am using a couple of canister filters and just purchased a protein skimmer.
My question is, are canister filter nitrate factories?
<It's complicated. Regularly cleaned (every 4-6 weeks, say) there's no particular reason a canister should produce nitrate. All it will support is filter bacteria and any insoluble organic matter trapped in the filter media. But beyond that the insoluble organic matter can start to decay, and that can eventually release soluble nitrogenous compounds. If regularly cleaned, you'd wash away this insoluble material (dead plant matter for example) before it released any nitrogenous material. Ultimately, any/all nitrate in the tank comes from the nitrogen that goes into the aquarium via
fish food. Normally, some percentage of that nitrogen would be in insoluble material and it wouldn't have any impact on dissolved nitrate in the water. But in a canister filter that hasn't been cleaned for a while, some of that insoluble matter is now entering the nitrogen cycle in your aquarium, ending up as nitrate. This is where the "nitrate factory" idea comes from.
It isn't magically synthesising nitrate from the water; that makes no scientific sense at all. Make sense? Contrast with live rock. Like a canister, the bacteria on the surface turn ammonia into nitrite and then nitrate. But unlike a canister, live rock contains bacteria in the tiny anaerobic spaces inside it that turn nitrate into nitrogen gas. So whereas an unmaintained canister can cause nitrate level in the tank to creep up higher than a similar tank with a well maintained canister, putting lots of live rock in a tank will normally pull the nitrate level down lower than a
similar tank with a well maintained canister filter. In short: a well maintained canister doesn't make extra nitrate from nothing, but neither does it lower nitrate as you'd expect from a big pile of live rock (or for that matter, deep sand bed or plenty of fast-growing floating plants)>
I see they are not preferred for salt water but are they ok for brackish water?
<Since live rock is a common option for marine tanks, yes, canister have fallen out of favour. But this isn't because they don't work. Clean a canister once every month or so and it'll not produce more nitrate than any other biological filter. But most people leave their canisters running for many months at a time (mine often run six months before cleaning!) and that can, in situations like that described above, lead to further decay of insoluble organic matter that releases soluble nitrogenous compounds into the water. They may even start supporting their own biota of invertebrates that consume food and excrete nitrogenous wastes; tubeworms, cnidarians and the like.>
If so, I may choose to raise the salinity in the future, at what point would a canister not be a good choice?
<Less a salinity, more a question of frequency of maintenance. Properly maintained, a canister remains a viable choice, particularly in fish-only systems where reverse-flow undergravels can provide exceptionally clean and
clear water as well as excellent oxygenation along the bottom for those fishes that prefer to stay down there.>
Thanks for the help.
<Most welcome. Neale.>

SW stocking & filtration      1/21/15
Hello there. I have a 125 brackish set up that I plan on converting over to saltwater in the next few months. The tank currently has the following:
1 green spotted pufferfish
1 ruby scat
8 mono Sebaes
2 Columbian catfish
1 white crayfish
<These aren't brackish.>
3 black mollies

As The salinity of the water gets closer to seawater (around 1.015) I plan on returning everything back to my LFS except the scat, both catfishes, and three of the monos.
<Cool. Though the Puffer and Mollies would be fine in seawater (though how long either would survive alongside a Volitans Lionfish is debatable! So your choice here is a wise one.>
Once I finally get the salinity to 1.022 I plan on introducing the following:
1 black volitans lionfish
1 red cigar wrasse
1 orange shoulder tang
1 black edged moray eel
1 African starfish
3 squirrelfish

<An interesting mix of fish. Do think about the Squirrelfish carefully though; many species are happier at slightly lower temperatures than some other tropical marine fishes.>
I was wondering if this would be too overstocked because if so, I can easily get rid of the monos and the catfish but the mono is special to me.
<That's a lot of fish for a 125 gallon tank! The Cigar Wrasse alone gets to some 50 cm/20 inches in the wild, so even a 200 gallon tank would be somewhat cramped. If this was me, I'd stock somewhat slowly. I'd skip echinoderms and other invertebrates, at least initially, because they're much more delicate (with a few exceptions) than marine fish. A Scat; a pair
or trio of Monos (they often form pairs that work rather well); the Shark Cats would make good "carry overs"; add to these the Lionfish (an excellent companion for robust brackish water species); a peaceful and easy Moray like Echidna catenata would be my next choice; then if you want something active and midwater-y, then perhaps a snapper, tang or even a robust
Angelfish. One of the smaller groupers can work too, but not many are scaled for life in 125 gallons.>
Also, I am currently running two MarineLand penguin 350 filters that have a combined flow rate of 700 gph so I was wondering if this would be sufficient in keeping up with the bio-load in the aquarium or would I have to upgrade to something bigger.
<Do let me direct you to Bob's article on stocking marines.
Various links from there. Much fun to be had with fish-only systems, but would recommend aiming for the FOWLR avenue at some point, canisters alone being okay but not great for marines. In such systems brackish species can make interesting additions; Monos as dither fish for shyer species, Shark Cats as centrepiece predators. Cheers, Neale.>

Tank circulation, Brackish Set-Up   Hi there, <Hello,> Your site is an inexhaustible resource! <Thanks for saying so.> I currently have multiple freshwater tanks running, and have zero saltwater experience (expect one tank that was low salinity brackish). When I purchased my first large tank (120 gallons) a few years back, my priority was good filtration. The tank has two built in overflows draining to a 40 gallon sump for filtration. It is all powered by a Blueline 40hd water pump that puts out about 600gph through 2 outputs. My experience has been that this is too much current for many freshwater fish, as many species I've introduced seem overwhelmed. <Hmm... does depend on the fish. Freshwater fish from habitats like mountain streams will be used to very strong currents. So things like Cobitid Loaches, Hillstream Loaches, numerous cyprinids, and some of the Loricariid catfish thrive in 'fast water' aquaria. On the other hand, Angelfish and Gouramis are fish from slowly flowing or still water habitats, and don't like too much current. In general, aim for turnover levels 4-6 times the volume of the tank for small to medium sized community tropicals, and 8-10 times the volume of the tank for fast water species as well as things like Mbuna that also come from high energy environments.> Currently I limit my stock to bottom dwellers like loaches, but I have a few other fish that are doing fine like rainbowfish and a couple cichlids. I will soon be moving and am using this as an opportunity to change some of the setups, so I have a few questions: 1. For my 120g aquarium, I was thinking about moving the inhabitants to another tank and going brackish. I would like to go with a fine substrate (sand) and get a few dragon gobies and add other compatible fish. My inclination is that the current setup has too much water movement, especially for a sand bottom. Should I get a water pump with less output, plumb in a valve to restrict flow, or find a way to diffuse the return so that it's not so concentrated (like adding another output to the tank)? For species less tolerant of current, is the idea to not stock the tank as heavily so you require less filtration and water movement? <Water movement actually doesn't shift much sand. What gets sand into the filter is the activity of the fish: if you have burrowing species (like Gobioides spp.) then sand can certainly be kicked into the filter inlet. There are ways around this, the simplest being putting rocks in the immediate area around the filter inlet, so there's no sand to be kicked that way. Adding a certain amount of fine gravel to your silica sand/coral sand mix will also help to stabilise it, and I'd also recommend placing a gravel tidy (basically a plastic flexible mesh cut to size) on top of one layer of substrate and then putting another layer on top. This [a] limits how far down the fish can dig; and [b] creates a permanent cushion of sand that can be relied upon to stop rocks slipping down and cracking the glass.> 2. The sump is an Oceanic brand sump set up so the returning water is dumped onto a drip tray, holding a filter pad, that sits over a tower of bioballs. The water then flows toward the sump output but first flows through another sponge. I guess my first question on this is if you've heard any complaints about oceanic making poorly designed sumps? <Can't comment; never used this brand, and not even sure they're available in the UK.> Even with a new piece of filter pad, the water mostly pours around the Bioball tower (very noisy and useless). <Don't knock Bioball filtration: it works rather well for the aerobic stages of biological filtration. Used this system during the early 1990s, for a variety of purposes, and was always impressed. A bit old fashioned by modern standards, but that's really more because Live Rock filtration also does the anaerobic part of biological filtration as well. There's nothing actually wrong with old fashioned wet + dry filtration.> To deal with this problem I was thinking about getting a larger drip tray and Bioball tower to sit beside the other tower. The other thing that bugs me about this sump is that just under half the bioballs are submerged under water. I would think this would cater to anaerobic bacteria that aren't going to do as good a job for my water. <I doubt any anaerobic filtration will occur here; even submerged under water, the bioballs will be in oxygen-rich environment since the water has just sluiced down the tower, mixing with air.> Should I try to remedy this? <For freshwater/brackish, not worth the effort. In both cases, water changes are a cheaper way to keep nitrate levels down, and to some degree you can fast-growing plants to remove nitrate and phosphate directly. Under bright lights, fast-growing floating plants are amazing nitrate magnets.> I was very disappointed with the initial set up instructions for the sump (or lack thereof). You are given the parts with no diagrams or anything. If I used only the parts they provided, I would have had to attach threaded to non-threaded and other such horrors. Are most people making DIY sumps nowadays? It seems this would give you much greater flexibility... <Many people do seem to make their own sumps. There's something in the upcoming issue of Conscientious Aquarist out in the next week or so about combining a sump with an algal scrubber. Take a look.> 3. Any use for a refugium with a low salinity brackish aquarium? <Not much, unless you have access to brackish water plankton. There are plenty of brackish water invertebrates, but you don't see them traded. For brackish water aquaria, the most fun can be had either creating a low salinity habitat with plants, or else a high salinity system modeled on a rocky reef or harbour. It's amazing what you can do with some rocks, oyster shells, barnacle clusters, and a tube of silicone glue. Do check out a public aquarium: they're often very creating when it comes to brackish/shallow marine habitat reconstructions.> I would enjoy plumbing one in but don't know what value it could add. <Extra water volume always helps, and above SG 1.010 you can use a skimmer, but beyond that, there's not a lot of advantage.> It would help with my high water output problem also... Thanks for your help! Paul <Cheers, Neale.>

Sump for Brackish F8  5/7/07 Hello Again, <Hi, Pufferpunk/Jeni here today.> For about a week I have had my 2" Figure Eight Puffer in her new 15 gallon home.  Don't fret, this tank was cycled with guppies before I put her into it for about 3 weeks.   <Good thing, cycling 1st but why should the guppies suffer?  It's very easy to fishless cycle.  Do a search on that at WWM.> Here are the parameters: Ammonia=0 Nitrite=0 Nitrate=10 Temp=77-80 F pH=8.0 SG=1.005 As I watch her, I don't really knew the gender, just guessing, I don't like the look of the heater and filter.  I was wondering if I could put a 5 gallon sump under the tank.  I have heard of these used alot in marine tanks just never in a brackish.  I figured I would just check with you because you have helped me so much in the past. <A sump can never hurt.  The larger, the better!  ~PP> Thanks

FW water quality, puffer 8/9/05 Bob, <Erik> Update and 2 quick questions for you... My tank appears to be cycled. Ammonia and nitrites are zero. Nitrates are between 20 and 40 PPM. I did a 50% water change yesterday to bring these down a bit. My tap water is not as loaded with Nitrates as I'd originally thought. Your comment made me rethink my original tests so I did a control and tested straight tap water, only 5 PPM nitrates. <Ahh> But I did notice one strange anomaly, and I double checked it several times to be sure, my tap water does appear to have ammonia in it! I did a control with distilled water, and of course it registered zero, the tank is registering just above zero, but less than .25 PPM, way less. The test tube appears pure yellow until I put a control of distilled water next to it. You can then tell it has a very slight green tint to it which indicates some level of ammonia. Am I correct in assuming that a control test of distilled water will always look a little purer than tank water? <Generally> There will always be trace amounts of ammonia in the tank because of waste that hasn't been converted by the bacteria yet correct? <Umm, no... not detectable amounts in a completely cycled system> Any way, I retested twice and yes, my tap water appears to contain between 1 and 2 PPM of ammonia! <Trouble> I'm going to try a different test kit, I find it hard to believe that the city would allow such high levels. I don't drink tap water anyway but I worry about the fish and my cat. He'll get bottled water until I find out what's going on. <A good idea> Anyway, my important question is this... Is it normal for a Cholonodon patoca (Milk Spotted Puffer) <Mis-spelled... Chelonodon: http://www.fishbase.org/Summary/speciesSummary.php?ID=6610&genusname=Chelonodon&speciesname=patoca> to spend quite a bit of time resting on the bottom? <Yes> When he moves, he's moving and healthy looking, but he rests quite a bit. I've seen you tell other puffer owners that they do this, but there is very little info out there about my little guy. As passive as he is, I'd expect the Milk Spotted Puffers to be more popular. Haven't seen him even threaten to fin nip his tank mates to date. I know this will change with age but he's pretty friendly right now, even shares his food with the sharks! Salinity is about 1.008 and I am gradually bringing that up so as not to hurt the other fish. Water temp is about 80 degrees F and the pH is about 7.6-7.8. Thanks Again, Erik <Keep studying... prevention... Bob Fenner>

Protein Skimmer In A Brackish Tank 7/29/04 HI <Hi there! Scott F. here today!> I have 375L brackish aquarium with 2 Green Puffers, 4 Figure-Eight Puffers, 3 Monos and two Scats. Specific gravity is 1.016, PH 7.8. I have a questions: Do I need protein skimmer in my aquarium?? <Well, a protein skimmer is a great device that can provide numerous benefits for captive systems. In lower "brackish" specific gravities, skimmer efficiency might be limited. However, since you are indicating that your system is running at 1.016, a skimmer should work> I'm thinking about WeiPro skimmer: SA-2012, SA-2013 and SA-2014. Which will be better?? Do you think that Atman AT-306 (2000l/h) will be enough for WeiPro SA-2013 skimmer? Please help me. P.S. Sorry for my English <Your English is fine! I have no personal experience with the skimmers that you are talking about, but my general rule of thumb is to go with the largest skimmer that you can practically run in your tank-and that you can afford! Good luck! Regards, Scott F.>

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