Substrate Poisoning Water?

[juhason]

I converted to a soil substrate, and included in the soil some potash, natural terra cotta clay, and dolomite/garden lime. Now my issue is that I keep getting air bubbles all over the place. I had air bubbles the second I set up the tank and poked the substrate around a bit, but I didn't think I would still have air bubbles now, about 3 weeks after set-up. I don't have that rotten egg smell or any sand turning black, but a few MTS snails died and a lot of them hang out above ground level, so I don't know if this is a toxic build-up. I got some cardinal tetras 2 days ago, but 4/5 of them died. (However they were not in the best condition when I got them, and I'm 90% sure they died of other reasons, cause I have an oto in there who is still hanging in). Do you think I have a toxic anaerobic build-up type situation or no??

 

[TwoTankAmin]

I suggest you test your KH and GH as calcium carbonate raises both of these and is also the primary ingredient of "garden lime."
 
Anaerobic substrate occurs because oxygen cannot penetrate. if you have plants in your substrate, they will bring oxygen from the water down to there roots and release it to oxygenate the soil. They do this to encourage the growth of bacteria that need O.
 
If you started with dry loose soil, then trapping air is not that unusual and it will take time for it to be forced out. Anaerobic pockets need to be disturbed to release their toxic gasses and you will smell them.
 
The denitrifying bacteria in tanks want anoxic rather than anaerobic conditions. They only make toxic gas in the complete lack of O. Normally, they work by extracting bound oxygen from nitrate. Anaerobic means no O, either free or bound. Anoxic means there is very little or no free O but there is available bound O. Remember, Nitrate is NO3, that is one nitrogen and three oxygen (those 3 Os are bound).
 
As long as denitrifying bacteria have bound O, they convert the nitrate in nitrogen gas which is basically harmless. However, once there is neither free or bound 0, these bacteria will use sulfates and when they do the result is they make hydrogen sulfide

Hydrogen sulfide (also known as H2S, sewer gas, swamp gas, stink damp, and sour damp) is a colorless gas known for its pungent "rotten egg" odor at low concentrations. It is extremely flammable and highly toxic.

from https/www.osha.gov/SLTC/hydrogensulfide/
 
Denitrifying bacteria are some of the slowest to establish in tanks (if they do at all) and usually require many months to do so.
 
You do not have anaerobic pockets or such bacteria in your tank this soon.

 

[juhason]

I suggest you test your KH and GH as calcium carbonate raises both of these and is also the primary ingredient of "garden lime."
 
Anaerobic substrate occurs because oxygen cannot penetrate. if you have plants in your substrate, they will bring oxygen from the water down to there roots and release it to oxygenate the soil. They do this to encourage the growth of bacteria that need O.
 
If you started with dry loose soil, then trapping air is not that unusual and it will take time for it to be forced out. Anaerobic pockets need to be disturbed to release their toxic gasses and you will smell them.
 
The denitrifying bacteria in tanks want anoxic rather than anaerobic conditions. They only make toxic gas in the complete lack of O. Normally, they work by extracting bound oxygen from nitrate. Anaerobic means no O, either free or bound. Anoxic means there is very little or no free O but there is available bound O. Remember, Nitrate is NO3, that is one nitrogen and three oxygen (those 3 Os are bound).
 
As long as denitrifying bacteria have bound O, they convert the nitrate in nitrogen gas which is basically harmless. However, once there is neither free or bound 0, these bacteria will use sulfates and when they do the result is they make hydrogen sulfide

Hydrogen sulfide (also known as H2S, sewer gas, swamp gas, stink damp, and sour damp) is a colorless gas known for its pungent "rotten egg" odor at low concentrations. It is extremely flammable and highly toxic.

from https/www.osha.gov/SLTC/hydrogensulfide/
 
Denitrifying bacteria are some of the slowest to establish in tanks (if they do at all) and usually require many months to do so.
 
You do not have anaerobic pockets or such bacteria in your tank this soon.

Perfect explanation, thank you so much!! I was getting worried cause my snails are being so strange about burrowing in the soil. But I'm glad its not that issue.But once again thank  you for enlightening me.

 I will check my KH and GH, but I did put a very small amount of garden lime, as recommenced by numerous online sources explaining soil substrates, and the soil I used has a little bit of peat moss in it which should hopefully balance that out. But thank you for the tip I'll check it out!