Compilation-Substrate: Its Pros and Cons, Problems and Solutions, Cause and Effect

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Viviendo la vida loca!
MFK Member
As some people have kindly pointed out, the previous thread has been long winded with over 16 pages so I have decided to make a compilation of the important points which I have collected below.

Lupin said:
Polyptasaurus;3199699; said:
If you choose sand, you need to put so thin of a layer that it really just covers the bottom of the tank, if its even an inch thick, its WAY too thick. what happens is that the sand traps nitrites/nitrates and if a certain patch of sand is left untouched for too long, upon disturbing it, it can actually create sulfuric acid in your water, instantly dropping your pH to 4 or lower and doing massive damage to your fish (obviously).

Get rid of your sand if you have it too thick, or simply take enough out so that you are only covering the bottom of the glass. The most effective way I've found is to use an 8 foot hose withOUT the big syphon tube on the end of it, and cut the hose at an angle. By cutting it an an angle you not only suck more sand out, but it doesnt get clogged as easily.
It is very common to think that cleaning the "crap" off of the top of the sand is all you need to do. But the filth actually settles into the sand if its thick and it stays there, rotting and creating more ammonia. With that said, some people will stir up the sand and THEN do a water change, thinking that the garbage will be sucked out, but you're actually less likely to get any of the filth out that way. That is why it is better to just suck the sand out, wash it, then put it back.
Could you please tell us how you have figured out the sand can trap nitrite and nitrate? Do you vacuum the organic wastes out of the tank at all? Sand is heavier than the wastes lying around so to say, nitrite/nitrate are trapped in there at all, is practically illogical.

With anaerobic pockets, the anaerobic bacteria break down nitrate into nitrogen gas which is then released back into the atmosphere. The only reason why we do not encourage anaerobic pockets in FW tanks rather than SW tanks, is the fact hydrogen sulfide does form in the process which is a powerful acid that is indeed capable of pH steep dives.

However, your paragraphs above do not find the right solution to counter those predicted problems. What you need to do here, is vacuum all the organic matters out of the tank and try to rake your sand to avoid dead pockets at the bottom. Heck, try to hire the trumpet snails to do the job for you. My trumpet snails aerate the sand for me and I have not had a single issue with my sand.;)

Believe it or not, sand ends up being MUCH dirtier than gravel and very annoying to clean. Best way to clean it is to syphon the sand into a bucket and actually wash the sand off, then dump it back into the tank. Even then, it should be done every 3 weeks.
Your perception does not share the perception of some of us. I use sand and gravel in all my tanks and the ones in sand are cleaner than the gravel as the organic matter doesn't get trapped among the gravel unlike the sand.

Your suggestions are unfounded and unnecessarily tedious. This is similar to total stripping off the whole tank which gives undue stress to the aquarium inhabitants.
swede;3199993; said:
sulfuric acid is a common active ingredient found in PH down. not saying this is a great product, but i am trying to say that its not like its going to turn your tank into a toxic dump. you would notice the drop in PH as well.
swede;3199997; said:
also, trumpet snails have been said to burrow in the substrate and reduce the pockets of gas
jschall;3200265; said:
There's NO reason well-maintained sand would facilitate the production of sulfuric acid in any quantity that could possibly effect your fish.

Sand isn't going to "trap nitrites and nitrates." It might trap waste which will decompose into nitrate, but the amount of waste that will end up trapped IN your sand, which is more densely packed than gravel meaning there's less empty space in it, will be negligible compared to what builds up in your filters over a week. Waste tends to sit on top of the sand instead of in it, so yes, it's easier to clean. Any nitrate produced from waste in sand is going to be removed the same way any other nitrate is removed - when you do a water change.

Millions of aquarists have used sand for many many many years. The fact that "polyptasaurus" has used faulty logic to come to the conclusion that sand is "bad" isn't going to change anyone's mind. Or maybe it will. Common sense ain't so common any more.
Pharaoh;3201182; said:
I will only add one thing to the discussion in response to the sand comments.

Leaving sand alone will allow pockets of gasses to form. Yes, you can leave a tank for a long time without stirring the sand. The issue comes about when that sand is finally moved. The gasses will enter the water column and you risk killing inhabitants of the tank. It is better to just stir it up once in a while to be on the safe side.
bluehairman;3201225; said:
Does this happen with fine sand only like alex suggested?
Pharaoh;3201357; said:
I would say it could happen with almost all sands. But I could never say 100% positively because sizes of available sand vary by name and actual size. But in most cases, yes it does happen with most types of sand as they are all compact enough to trap harmful gases.
velanarris;3201715; said:
Guys, the whole trapped gas issue is not just sand. All substrates can have pockets of anaerobic bacteria due to compression. The substrate compresses down over time PREVENTING oxygenated water from penetrating small pockets of your tank. These anaerobic bacteria excrete hydrosulfane gas, which in water becomes sulfuric acid.

In order for this to be a problem you need to be truly terrible at maintaining your tank and have livestock that do not dig, shift, or disturb your substrate at all.
Bderick said:
Davey_8313;3199923; said:
:thumbsup: the most informative post in that thread below

Pufferpunk;1327441; said:
The anaerobic bacteria live in areas devoid of oxygen, such as deep in the substrate of the aquarium or in areas where decorations cover the substrate. Some of the anaerobic bacteria are beneficial; some of them convert nitrate into nitrogen gas. This is why most denitrators have such slow flow rates and long coiled tubes- the idea is that bacteria will colonize the first part of the tube or denitrator and consume all of the oxygen, so everything from that point on will be anaerobic. In large quantities, anaerobic bacteria are bad because some types produce hydrogen sulfide as a metabolic byproduct. Hydrogen sulfide smells like rotten eggs; in marine aquaria, just stirring an anaerobic pocket can kill the fish. In freshwater it is largely less toxic, but is a symptom of poor husbandry techniques. These anaerobic areas also indicate lost bio filter real estate. Some of the other byproducts of anaerobic respiration are toxic if allowed to build up, but hydrogen sulfide is the most noticeable. The main way to fight anaerobic areas are to avoid placing rocks and decorations in a way that water cannot flow over the surface of the substrate. Decreasing substrate depth or increasing particle size will allow more oxygen to go deeper in the substrate. Fine sand has a tendancy to get packed and turn anaerobic; livestock ranging from Malaysian livebearing snails to horseface loaches to eartheater cichlids to (small) softshell turtles may be needed to prevent anaerobic pockets from forming.
kzimmerman;3201062; said:
HEHEHEH!, when will you FW peoples get the drift from the reefers? Sand, in DEEP beds, at least 3-4 inches, can be VERY beneficial to a tank. It provides room for nitrates to be denitrified into harmless stuff, mostly free nitrogen and water, I think, and provides for better root growth in planted tanks. The secret to keeping the sand clean is to utilize a cleanup crew, just like the reefers. Introduce some tubiflex worms, not alot, but some, befor you stock the tank. Add some snails, as mentioned earlier, and you won't need to continually stir up the sand. The worms and snails will take care of that for you.
Hope this helps.
*Alex*;3201090; said:
hehe nobody has mentioned the fact that there isnt just one type of sand......!!!!!! Sure if you get very fine sand it will mess up your tank.... it will clog filters,, it will compact quickly and will not provide oxygen to plant roots... and cus the gass bubles to form ect ect blah blah( to be honest id say the only way these bubles could be very harmful is if some1 took a pile of **** stuck it under the sand and left it there without stiring it up..)i know here in Ireland alot of people get playsand because its very cheap... And it never works out. I just use Aqurium sand i got from my LFS its more expensive but its perfectly fine.... It doesnt cloud up water and go into filter even when my 13" Plecos decided to go a bit crazy..... It anchors the plants roots and lets oxygen reach them! Sand is perfectly fine in aquariums... Just dont get fine sand...(well Depends of setup)! Sicila Sand is very good,,,,!
nc_nutcase; 3202118; said:
Jamieishard;3201762; said:
i just want to say i hate sand for aquariums...its always a mess to deal gets everywhere....its got into every filter i have ever put on a tank with sand..and i finally had enough and python syphon shot a good 100 bucks worth of sand into my back yard...never again.. but thats just IMO
Jamie, I am absolutely NOT saying you should be using sand. They are your tanks and do whatever makes you happy with them... But it is fair to mention in response to this that grain size of the sand can make all the difference. The pretty colored sand sold at most LFS's labeled "Aquarium Sand" is typically very fine grained and often causes such problems. Using a larger grained sand will highly reduce the potential for filter damage... also prefilters can be used to prevent sand from ever entering the filter...

Since you had $100 worth of sand I can only assume you bought the over priced "Aquarium Sand", as Pool Filter Sand or other industrial purpose sands (the larger grained stuff) is usually around $4~8 per 50 lbs, making $100 worth or it more than even the most monstrous fish tanks would need.

black_monster;3201968; said:
i can somewhat agree that sand does trap nitrates because if uneaten food or poop gets trapped in for awhile, it will cause ammonia spikes. this happens to me a couple times a year
As mentioned previously… waste is lighter than sand and the gaps between sand particles is smaller than even exceptionally small waste particles… therefore it is unlikely to “settle” into the sand…

The gaps between pieces of gravel are MUCH larger than gaps between sand particles and does allow waste to fall into the gravel. So the problem of waste rotting in gravel causing an ammonia spike is far greater than the same thing happening with sand.

Sure you can gravel vac… but simply put, you will never be able to get all of the rotting waste out of the gravel through conventional gravel vacuuming… then consider the time/effort of siphoning waste off the surface of sand and giving it a quick stir to doing a gravel vac… It’s much easier to keep a sand bottomed tank much cleaner…

Lastly, I won’t quote anyone on this as many posters have made this error… Sand “can” compact and allow gases to form… it is not true nor fair to say sand “does” compact and allow gases to form… Myself an many other hobbyists can speak from personal experience that this is an exceptionally rare, yet possible, thing to have happen in a fish tank… and in those rare situations that it does, it is due to user error (typically deep sand beds AND not disturbing those sand beds for an extended period of time).

I agree this thread is just silly… yet I feel compelled to defuse misinformation or poor guidance… I completely agree we can make poor decisions when using sand and cause problems… but the sand didn’t cause the problem, the poor decision did… So proper education is the solution, not using gravel…
beblondie;3203746; said:
apparently people who get sand in thier filters don't know to rise the intake slightly
or use a prefilter on the intake
12 Volt Man;3204118; said:
borderraider;3203862; said:
i just spent the last hour searching through online chemistry journals and my university chem sites and cant find anything to support the OPs argument. I would be really intrigued to see which research papers his sister reads to provide evidence. Could the OP or his sister via himself please cite a source, purely out of scientific curiosity?

I came into this thread late, but I believe part of the problem here, is that what is being said about sand specifically is applicable to ANY substrate, not just sand.

ie any substrate can trap detritis if not cleaned properly, which is then broken down by bacteria as part of the nitrogen cycle.

like gravel, if detritius if left undisturbed, there is the potential for anaeroblic conditions to exist which facilitates a great envionrment for anaerobic bacteria to thrive.

these anarerobic bacteria reduce nitrates back to nitrites, releasing nitrogen gas in the process, which can be seen as bubbles in the substrate when disturbered..

but this phenomenon is NOT unique to sand or gravel.

it can happen in any substrate if conditions are allowed to exist..
Bderick67;3204161; said:
12 Volt Man;3204125; said:
the part about sand 'trapping' nitrates/nitrites is not correct, but its more of a wording problem.

sand or gravel both can accumulate detritus which as I mentioned, is 'food' for oxidizing bacteria (the good kind for us).

but they don't accumulate the byproducts of bacterial metabolism directly.

the bacteria do their thing, and the byproduct of which is nitrates in the aquarium water..
the so called "food" for your oxidizing bactera is also a food for anaerobic bacteria, but the byproduct is hydrogen sulfate(bad news). Basically though if there is no waste trapped in the sand there is no problem. Hydrogen sulfide can not be produced without a carbon source(trapped waste).
vladfloroff;3204175; said:
So are you suggesting that the OP is correct and sulfuric acid is created in the aquarium?
Technically yes it is but a very small amount. When the HS bubble rises to there surface there is some (very small) gas exchange at the edges of the bubble. Now if this bubble get pulled into you filter you will create much more H2SO4 and you can damage you bio filter as well.

This will happen with any medium be it sand or gravel if the material is left undisturbed for too long.
12 Volt Man;3204189; said:
can someone clarify this:

when nitrate is reduced via bacteria back to nitrite, the byproduct released is nitrogen gas (I work in wastewater treatment this can occur at the bottom of settling tanks)

this is how denitritors work in an aquarium

is H2S also produced?

I am thinking you probably get both - nitrate reducing bacteria (which give off N2 gas) and sulphur reducing bacteria (which give off H2S (hydrogen sulphide)

N3 gas is harmless to us and our fish.

H2S of course, is highly toxic..
Bderick67;3204202; said:
Interesting so there is actually oxidization of the H2S to create sulfuric acid?

Yes if there is a carbon source present you will get H2S
12 Volt Man;3204206; said:
It is a reduction.

chem buffs will remember: LEO the Lion says GER

Lose Electrons Oxidize
Gain Electrons Reduce
12 Volt Man;3204207; said:
so your always going to get some then. any detritus will have proteins etc which are carbon based..
Bderick67;3204217; said:
Probably true but it will need to be trapped in the sand where no oxygen can exist. So strirring the sand could actually cause more detritus to be trapped, possibly adding to the problem.
vladfloroff;3204223; said:
Proteins contain sulfur as well as carbon. Fish is high in sulfur as are eggs hence the strong smells associated with each as they age.
12 Volt Man;3204359; said:
true, but not all proteins contain sulphur. only those that contain sulphur containing amnino acids in their R group (like Cysteine) will.

this thread is turning into a biochemistry refresher lol
Lupin;3205287; said:
Every living thing has anaerobes in it, not just aerobes. Although in humans, anaerobes are often responsible for sinusitis, tetanus, dental absesses and many other health problems, they also play an important role in body functioning such food digestion. My point here is, that not all anaerobes are as bad as this thread made it sound to be nor is it that living beings do not have them in them which is one of the few points to consider.
Ali1;3205691; said:
Okay fellas, I emailed this concern to my bio professor I'm doing undergrad research with.

this is his reply :

Great question. I have mud on the bottom of most of the tanks in 101,
and in fact, it does trap anaerobic deposits. Sand does a fair job of it
too, especially the fine stuff. Whenever I clean out, or stir, one of
these aquariums, I get a little whiff of hydrogen sulfide. so, yeah.
thing is, I have never ever known fish to be harmed by it. Can you
imagine? In the wild, if a little bubble of swamp gas killed fish?
I don't know what you are keeping, but the usual aquarium species can take a
little harmful gas.
12 Volt Man;3205798; said:
problem is, fish living in a lake/river are living in billions of gallons of water.

fish living in our tank live in under 200g most of the time

so his analogy about the swamp gas a bit faulty..the level of dilution of toxic byproducts of bacterial metabolism in the wild makes them negligable.

not so in our tanks..

that being said, chances are most of us on this site will never see these problems because we all do regular maintanence of our tanks.

its the people that leave their tanks for months without touching them that are at risk for problem with 'dead pockets' in gravel or sand..
Lupin;3206048; said:
My thoughts exactly.:iagree: There is not much to compare between a large body of water and a glass box. The glass box is under our responsibility. The former is under Mother Nature's care, never mind if human activities often interfere with it.
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