My Pool filter sand is black?

[Diego21]

Ok I have a weird question, I use pool filter sand for my tanks. I was doing my weekly water changes in my grow out tank today and while I was sucking the crud out I disturbed the substrate and noticed that under the top substrate the sand was starting to turn black! Is this normal? What is it? BTW I have about 45 fry in there about 1/4 in long and one snail.

 

[manbeast]

sounds like you've got some nasty bacteria brewing, do you have anything in there to keep turning the sand over like MTS, they love to burrow in the sand keep it from getting stagnant, I have heard that if you intend to try to clean it up you shoul do small sections at a time as not to release to many toxins at once, best of luck

 

[rocksor]

That's anaerobic bacteria growing underneath. You can get rid of it by vacuuming only small sections during your water change. There maybe hydrogen sulfide gas in there which will be deadly to fish if too much of it is released. Once you get rid of all of it, sift the sand at least once a week using the gravel vac.

How thick is your sand bed?

 

[Diego21]

About 1 1/2 in deep, should I try to add more filtration? I have a sponge filter in there now

 

[manbeast]

I just like to use Malaysian trumpet snails myself they really do a good job, bu I understand if you don't want snails in your tank se people just don't like them

 

[Mogurako]

Either stir it yourself when doing water changes or add size appropriate catfish or loaches to dig around. MTS get out of hand crazy fast and can get to be rather unsightly. Mine spend most of their time above the substrate even when the lights are on.

 

[Diego21]

Hmm, def some things to think about. I have one snail in there now but I forgot what he is called. He is about the size of a big gum ball and brown but he doesn't dig through the substrate, just cruises the top and the glass. I am not sure if I can have catfish or loaches in my tank because it's my fry tank, that's why I chose this snail cause I didn't want anything eating my fry. The snail also doesn't reproduce in aquariums, thats what I remember reading anyway any options on fry friendly substrate diggers?

 

[Mogurako]

Your fingers

 

[HUKIT]

That's anaerobic bacteria growing underneath. You can get rid of it by vacuuming only small sections during your water change. There maybe hydrogen sulfide gas in there which will be deadly to fish if too much of it is released. Once you get rid of all of it, sift the sand at least once a week using the gravel vac.

How thick is your sand bed?

Anaerobic gas pockets are present but they are harmless, as the bacteria start transforming due to the lack of oxygen they start reducing iron and sulfur, one of the by-products of this is hydrogen sulfide which is truly dangerous but when exposed to oxygenated water it's utterly harmless. There is not one documented case of anaerobic gas pockets causing harm or a fatality in a aquarium, another perpetuated myth reguritated on aquarium forums.

 

[jetajockey]

I have to agree with that. I've heard some horror stories that come shortly after upturning a deep and long established substrate bed, but there's a myriad of other issues (including nutrient overloads) that could easily be the cause of the nuke.

There's also some people that intentionally do DSB (deep sand beds) in FW. Also, MTS typically stay in aerobic areas while scavenging, they don't usually venture into true anaerobic areas, so they may help some, but won't cure the ultimate cause.

 

[Diego21]

Wow, thanks everybody! Every time I start a thread in this forum I truly learn something new each time. There is such a wealth of knowledge and it is slowly making me a better aquarist thanks again

 

[jcolon]

Yep .. Agree with Hukit and JetaJockey.

 

[rocksor]

Anaerobic gas pockets are present but they are harmless, as the bacteria start transforming due to the lack of oxygen they start reducing iron and sulfur, one of the by-products of this is hydrogen sulfide which is truly dangerous but when exposed to oxygenated water it's utterly harmless. There is not one documented case of anaerobic gas pockets causing harm or a fatality in a aquarium, another perpetuated myth reguritated on aquarium forums.

ok. so is there enough oxygen in water to render it harmless? From reading this it sounds like you need a pressurized oxidation system and longer contact time in water to have it react to H2S.

Removing Hydrogen Sulfide Gas through Pressurized Oxidation

So, when you release H2S from the gravel, it just bubbles out of the aquarium because there is not enough oxygen in aquarium water nor enough contact time with the water for it to harm the fish.

 

[jcolon]

ok. so is there enough oxygen in water to render it harmless? From reading this it sounds like you need a pressurized oxidation system and longer contact time in water to have it react to H2S.

That pretty much sums it up ... I asked the chemistry teacher at my school about this last year. Your typical aquariums just don't have a large enough and or deep enough sand substrate to produce enough H2S to be lethal. Plus, there's usually enough Oxygen in the water to oxidize any escaping H2S quickly because there's so little produced.

Well water I'd imagine presents a bigger issue as they are much deeper and more deplete of Oxygen. Similar issue with Green Lake State Park in Upstate NY. It has no circulation so the bottom part of the lake is an Anoxic zone with Purple Bacteria ... while the upper part can support life.

Still .. I bookmarked the article for discussion with my students when we discuss well and groundwater.

 

[Diego21]

Well, the only thing I have running is two sponge filters, one on each side of the tank. It is a pretty strong airstone running the filters.

 

[jcolon]

Well, the only thing I have running is two sponge filters, one on each side of the tank. It is a pretty strong airstone running the filters.

Sponge filters ... even with strong air-stones don't generally produce much of a current / circulation. Still even with the most powerful filters ... Sand substrates will still have anoxic zones since their pore spaces are much smaller.

 

[Diego21]

Ok, so to break down all the scientific talk ( which is really interesting by the way ) I need to create more current in my tank and regularly soft my substrate?

 

[Mogurako]

Hukit and Jetta both stated they are harmless, they will occur even with more flow. If you noticed them when you're doing water changes just stir them up with your siphon.

 

[jcolon]

Hukit and Jetta both stated they are harmless, they will occur even with more flow. If you noticed them when you're doing water changes just stir them up with your siphon.

+1 .. I stick my gravel vac into the sand ... with PFS a gravel vac generally isn't strong enough to completely suck up the sand into the tubing, but it lifts it high enough to stir it up really well.

 

[Mogurako]

+1 .. I stick my gravel vac into the sand ... with PFS a gravel vac generally isn't strong enough to completely suck up the sand into the tubing, but it lifts it high enough to stir it up really well.

Exactly what i do as well, works wonders.