Is 5 inches of sand substrate too deep?

[otterblue]

Hi. I keep reading conflicting reports about the danger of having a deep sand bed. Mine is about 5 inches deep, with a small amount of gravel at the bottom (long story). I was concerned about a "methane catastrophe" killing all my fish.

It's a 55 gallon tall with cories, ember tetras, neon green rasboras and Amano shrimp, No snails. Moderately planted with temp. around 78*F.

Thanks for any advice!

 

[FishHobby99]

I have sand that deep & deeper in some sections of the cichlid/catfish tank because they shove it around & make gullies & hills. I leave it be. That’s what these excavators love to do.

Never heard of a methane catastrophe !

 

[FishHobby99]

Well. There was this one time when my brother & his friends were lighting farts, but that’s a hole different thing…..

 

[Byron]

If you do not disturb it, you will not have problems with poisoning fish. If on the contrary you regularly disturb it significantly, you also will not (should not) have problems. Whether the fish do the disturbing or the aquarist doesn't really matter. The following excerpt from an article I wrote on bacteria some years ago may be instructive.

Substrate Bacteria​

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The greatest population of bacteria in a healthy balanced aquarium occurs in the substrate, not the filter. The floc or humic compost that collects in the substrate is the host for the biofilms; this is why the substrate in planted tanks should never be disturbed significantly, and many aquarists apply this to non-planted tanks as well.​

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In very general terms, aerobic nitrification takes place in the top 1-2 inches of the substrate; anaerobic de-nitrification takes place approximately 2-4 inches down, and anaerobic bacteria producing hydrogen sulfide occurs in substrates deeper than 3-4 inches. In all three cases, it will be deeper in coarse substrates (like pea gravel) and more shallow in finer substrates such as sand. These generalities will also vary with the presence of live plant roots and substrate “diggers” such as snails and worms, since these factors result in more oxygen being made available in the substrate, reducing anaerobic bacteria activity. An oxygen level in the substrate of as little as 1 ppm promotes nitrogen reduction rather than sulfur reduction (hydrogen sulfide). [6]​

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Maintaining a substrate of fine gravel or sand no deeper than 4 inches, having live plants rooted in the substrate, and keeping Malaysian Livebearing snails are the best and safest methods of providing a healthy biological system for aerobic and denitrifying anaerobic bacteria.​

 

[Sgooosh]

I have sand that deep & deeper in some sections of the cichlid/catfish tank because they shove it around & make gullies & hills. I leave it be. That’s what these excavators love to do.

Never heard of a methane catastrophe !

If you do not disturb it, you will not have problems with poisoning fish. If on the contrary you regularly disturb it significantly, you also will not (should not) have problems. Whether the fish do the disturbing or the aquarist doesn't really matter. The following excerpt from an article I wrote on bacteria some years ago may be instructive.

Substrate Bacteria​

​

The greatest population of bacteria in a healthy balanced aquarium occurs in the substrate, not the filter. The floc or humic compost that collects in the substrate is the host for the biofilms; this is why the substrate in planted tanks should never be disturbed significantly, and many aquarists apply this to non-planted tanks as well.​

​

In very general terms, aerobic nitrification takes place in the top 1-2 inches of the substrate; anaerobic de-nitrification takes place approximately 2-4 inches down, and anaerobic bacteria producing hydrogen sulfide occurs in substrates deeper than 3-4 inches. In all three cases, it will be deeper in coarse substrates (like pea gravel) and more shallow in finer substrates such as sand. These generalities will also vary with the presence of live plant roots and substrate “diggers” such as snails and worms, since these factors result in more oxygen being made available in the substrate, reducing anaerobic bacteria activity. An oxygen level in the substrate of as little as 1 ppm promotes nitrogen reduction rather than sulfur reduction (hydrogen sulfide). [6]​

​

Maintaining a substrate of fine gravel or sand no deeper than 4 inches, having live plants rooted in the substrate, and keeping Malaysian Livebearing snails are the best and safest methods of providing a healthy biological system for aerobic and denitrifying anaerobic bacteria.​

yes the chiclids disturb sand often so the sand does not produce gases right?

 

[itiwhetu]

All the reasons that @Byron give are the reasons I don't like sand in freshwater tanks.

 

[Colin_T]

Have enough sand to keep the plant roots anchored down.

In my opinion, 5 inches of substrate is a bit much, regardless of if it's sand or gravel.

 

[FishHobby99]

not understanding you, @Bryon. Are you saying never vacuum the substrate? Sounds kinda crappy.

 

[Byron]

yes the chiclids disturb sand often so the sand does not produce gases right?

I think you missed my point...what I was suggesting is that you can regularly disturb the substrate to keep it oxygenated, or if you have fish that do this it will be regular, and that's fine. On the other hand, if you leave it alone, and do not have fish doing it, that will be fine. But the irregular digging into a substrate that has been left alone for say weeks is where trouble can occur. I never touch any chunks of wood or rock, and anaerobic areas usually form under these; but if I leave them alone, all is well because de-nitrification is an important part of the whole picture.

A few weeks back we had a thread from a member who decided to leave the fish in the tank when removing the substrate to change it, and when the "dead" spots were disturbed, fish died.

not understanding you, @Bryon. Are you saying never vacuum the substrate? Sounds kinda crappy.

In some tanks I never disturb the substrate, and I have smooth sand in all my tanks. The Corydoras tank has never had the sand touched, when it was a 5-foot tank with 4-5 inches depth, or in the 70g with 3 inches, or now in the 40g with 2 inches. Cories continually dig into the sand, and without question these tanks had/have the cleanest substrates. You've seen photos in other thread of the incredible plant growth. If things are balanced, the less we interfere the better.

I do some vacuuming in the 29g which has my pygmy cories. For some reason mulm accumulates in that tank even though there are so few fish, and I feel it better to siphon some of it off (open areas only) for the health of the pygmies. But I never dig down into it beyond the top 1 or 2 cm.

 

[FishHobby99]

Thank you for the clarification, Bryon. I’ve been sick in bed for a few days & my mind is foggy.