DSB for freshwater

DSB of sufficient depth for the grain size will go to full anoxia in either water condition. The gases generated in the anoxic levels should do no harm in an intact and undisturbed bed in either condition - as they migrate upward, they should be oxidized and rendered harlmess. (even the ammonia produced in denitrification will not escape the substrate, it is oxidized if it migrates upward. N2 gas is not, there are not enogh nitrogen fixing bacteria in FW or apparently in SW substrates to attack it so it bubbles out - but is harmless). But if distrurbed, esecially massive disturbance, all bets are off - the situation in the earlier thread.

There are other potential issues in either water condition - fusion of the calcareous sand in SW plenums or DSB, excessive organic build-up in planted FW. But those are different from the gas generation/release issues.
 
Last edited:
This is interesting material, and RTR always makes it richer and clearer.

Let me throw in two perceptions, ready for correction-- like my former misunderstanding about ammonium/ammonia conversion in the linked thread.

1. There's no value to a substrate deeper than what the rootzone requires. And aquatic plant roots tend to spread into a mat rather than delve deep into anoxic zones.

2. Troubles come not so much from the naturally low oxygen levels-- hypoxic to anoxic-- as from the biodegradable "enrichments" down there. A good way to get high cation exchange capacity, beneficial to plant roots, without adding organics to decay and release H2S and stuff, is with lateritic clays, either baked or unbaked.
 
WetnamNY:
1) You already know my feelings & experience re rootzones - in every tank I've planted it has been the entire depth of the substrate, however deep that is on the particular tank. I have broken down tanks where the bottom glass looked like it had a fitted mat - all root. Very like a decade-old houseplant which has not been repotted. I haven't yet had a substrate in a tank deeper than the rootzone. Even my all-Anubias plenum tank has roots in the plenum- not a mat, but roots.

2) IME & IMHO, CEC is good but limits are undefined on either end. There are periods when folks get CEC-intense, but nobdy has shown exacty what range is good or bad. Gravel, especially coated gravel, is poor, but older tanks with gravel grow plants just fine. The mulm (organic and inorganic) fills in quite well to a point. Excess organics are bad when deep in the substrate, and old dead plant roots can produce that over time. The time frame involved depends on the particular plant cultivar. Vigorous crypts take ~3 years IME, swordplants about the same, Val (even Jungle) may not take as long but does not ever seem heavy enough to produce the notorious anoxic pockets, etc.
 
Originally posted by RTR
DSB of sufficient depth for the grain size will go to full anoxia in either water condition. The gases generated in the anoxic levels should do no harm in an intact and undisturbed bed in either condition - as they migrate upward, they should be oxidized and rendered harlmess. (even the ammonia produced in denitrification will not escape the substrate, it is oxidized if it migrates upward. N2 gas is not, there are not enogh nitrogen fixing bacteria in FW or apparently in SW substrates to attack it so it bubbles out - but is harmless). But if distrurbed, esecially massive disturbance, all bets are off - the situation in the earlier thread.
Click to expand...
Just a thought as to how the mystery gas release may have happened in the other chaps tank. Perhaps a buried rock, driftwood or other ornament prevented the gas from leaching out gradually as described above. It built to the point that it released all at once and then caused the catastrophe. Just a thought.
 
You must log in or register to reply here.
AquariaCentral.com
Top Bottom