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FAQs on Brackish Substrates

Related Articles: Brackish Components, FAQs on Brackish Salty Water, Brackish Water System Set-up Brackish Water Aquaria: 20 Questions; Yours Questions Answered by Neale Monks

Related FAQs: Brackish Filtration, Brackish Water Systems in General, Cycling a Brackish System,


Substrate sand....small brackish  - 12/02/2012
One more quick question before I disappear again for a while.....
I plan to put the two baby 1/4" balloon mollies into a true brackish environment.
I will acclimate them gradually of course.
<No need. Assuming specific gravity is going from freshwater (SG 1.000) to low salinity brackish (SG 1.002-1.003, ample for Mollies) then you can literally dump them into the tank!>
(They were kept with aquarium salt before I knew better. I plan to use the marine blend salt this time, and I'll use the meter to check the salinity.) I decided to do the brackish in a smaller tank that I have, and then I'll restock the 29 gallon with another type of fish to start out.... I'll probably choose the simplest kind of fish for the 29 gallon this time around.
I'm interested in using sand in the brackish tank. I read your article on WetWebMedia on substrate, and I also read this other article that gets a little more in detail on the handling of sand substrate on a cichlid site:
I like the idea of sand for the look, and it's nice for the small shrimp that will be the 2 baby mollies' only tank mates in the smaller tank. Black sand seems cool.
<Can be; shop carefully though. If you plan on adding any digging fish (say, gobies) then some "sharp" black sands, like Tahitian Moon Sand, aren't ideal. On the other hand, midwater fish and shrimps will be fine with whatever black sand you choose.>
Fish tend to like a dark substrate and it's attractive. Though, I also like the idea of coral sand that you mentioned in your article which is excellent for buffering.  White also sparkles nicely.
<But yes, with freshwater fish, the colours fade a bit. Not an issue with Mollies since the colours are hard-wired into them, but it's noticeable how (some) cichlids for example "fade" in tanks with a white substrate. Not all by any means, but some species.>
Either color works for me.  (I just don't have undergravel filter like you suggest though, I use a regular submersed one.  So it could work out differently I suppose….) (Would coral sand be too bright for mollies and shrimp, would it be likely to stress out my fish?)
<Will be fine. For one thing, the sand de-colours with age, becoming more off-white, even greenish.>
Also, the that stuff this guy in the cichlid article mentions about gasses building up worries me a little, I don't know.....  !  You have to disturb it periodically.  As I'm a beginner, I don't want to mess up the tank's chemistry accidentally!  Sounds like he is not afraid of it though.
<Quite so. The "deadly gas in the sand" idea is mostly a myth. It's theoretically possible if you have, say, 8 cm/3 inches of sand. But if all you're doing is adding enough sand to cover the glass, then gas isn't likely to accumulate to any great degree. Even where deep sand beds *are* used, this deadly gas problem just doesn't seem to happen, and in fact, there are positive benefits to deep sand beds!>
SO, my questions for you regarding a proper substrate are:
1) would mixing a little coral sand with fine gravel like you suggest avoid a buildup of gasses that using a straight coral sand for substrate might incur?  Maybe this is the simplest approach that would give me some sandy look, but be lower maintenance than a thick sand bed that tends to compact in the absence of burrowing species?
<Personally, I'd go with 2.5 cm/1 inch of sand, maybe with some coral sand stirred in if you want. Easy to clean and risk-free.>
Or--2) would using a bare minimum of coral sand, or even just the black sand, and just using it in a thin layer (perhaps 1/2 inch) and then stirring it a bit weekly, help to avoid a gas buildup under the sand?  My main concern with sand substrate is if I accidentally allowed too much gas to accumulate and then the fish become ill or die.
<Just doesn't seem to happen. The deadly gas is hydrogen sulphide, but in practise, this gas becomes oxidised so readily when it emerges from the sand that it's hard to get enough in the water to stress fish. Look at ponds; they have thick, anoxic mud, yet the fish are fine.>
It sounds like the trick to vacuuming sand is to stay a half inch above....maybe I could disturb the sand all around, and then wait till it settled and do the vacuuming about an hour later to catch excess debris I stirred up?  Or is there some important reason that the article I read says you should wait 8 weeks in between disturbing the sand substrate?!?!
<I have no idea. I don't bother. I put the sand in and leave it there. But I do tend to use snails and/or plants to keep the substrate biologically "active".>
Those are just guesses of mine, but you know the actual science...I feel that possibly using sand sparingly with regular agitation might be a lower maintenance and safe way for a beginner to work with sand, but I don't truly know. With gardening I've always strived to take the easiest approach.  Perhaps that really IS just plain old gravel in fish keeping.
<Can be. But sand has definite plusses.>
But if there's a way for a beginner to keep sand without a lot of trouble, I'd like to try it in my smaller brackish setup.
<Hmm… do read more on substrates, here:
Cheers, Neale.>
Re: Substrate sand....small brackish  - 12/02/2012

Thanks, this is very helpful.
Have a nice week and happy holidays too.
<You too, Neale.>

BW Substrate Questions  5/5/07 Thanks for the help again. <No problem!> I have gotten a root from PetSmart today and it looks great. I am going to go with the crushed coral to help  buffer the PH and also I like the bright colors of my GSP. That is when I realized I had a couple more questions. The first is: how to I calculate how much of the crushed coral I will need in lbs? My aquarium is 30long x 12 deep x 18 tall. <About 1lb/gallon.> The second is: I bought a few plants online and noticed they have a ceramic base to them, are they ok to use in the tank. <Shouldn't be a problem.> My last question is: When I change to the crushed coral should I leave some of the old gravel underneath? <I wouldn't.  Change it all out.> Once again thank you all, I get tons of info for myself and for my daughter's freshwater and I always recommend you all to anyone I run into that needs some help. Thanks again and keep up the great work. <Glad we're so much help to you & your young'n!  ~PP>

Old Florida Crushed Coral Safe For Brackish Tank?  2/14/07 Hello, <Hi Tom, Pufferpunk here> I love your site! Could you tell me if it is alright to use Florida crushed coral (the bags are about 20 years old, from a saltwater system I was going to do that long ago, and didn't)? It is white, not like the yellowish substrate they sell now. <I don't see why not, as long as it hasn't been used before.  Make sure you rinse it well, to avoid too much clouding of the tank.> I'm planning to have 1 mudskipper and 2 or 3 small mangrove seedlings I have (I have a bunch of seedlings I grow in pots around the house in fresh water) in a 20 gallon aquarium. <Make sure that tank is a 20 long, not a 20 high.  A 30g would be even better.  Try for one of the smaller species of mudskippers.  I always worry about a skipper climbing up the mangroves to the outside.> Would you suggest just rocks to build up a beach effect for the fish or what? <Rocks are fine.> I have  a few flat rocks that look like red sandstone (or at least they are dark red and heavy) and one that looks like something out of a King Kong movie (the rock formation he dreams of. :-) Do you think these are safe for a brackish system? I tried splashing plain vinegar on them and didn't see any bubbles (remembered from Earth Science days in High School a million years ago). <Sounds OK to me.> What would be some alternatives? Thanks for your time and again I love your site! <If you wanted to set it up for biological filtration, find something to hold gravel back behind the rockwork & bury a powerhead with a prefilter attached under crushed coral/gravel, making a waterfall from the output.  This looks great but would need to be torn down & cleaned every 4-6 months.  The larger the tank, the less poop will clog this system.  This is the powerhead I was thinking of: http://www.bigalsonline.com/BigAlsUS/ctl3684/cp18554/si1382178/cl0/marinelandpowerhead660r  ~PP> Tom

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