So, our 7.5gal (12x12x12) cube has been up and running for about 6-7 weeks and it hasn't been going well. Not only has plant growth been anemic at best, but despite being fully cycled it seems to kill off livestock quite rapidly. We've lost a batch of RCS (within two hours of introduction), three Nerite snails (a few days), a much smaller batch of Amano shrimp (one of them lasted about 60 hours), and even a batch of Malaysian Trumpet Snails (lasted about a week during which they seemed normal, but now none of them have moved in 48 hours). We've managed to create a surprisingly efficient death machine.
So, clearly there is something very, very wrong. We are not new to aquariums, so we do know how to do introductions and the tank is fully cycled (tested every day). (We use Seachem Prime as our dechlorinator.) And thus, we're at a loss.
Here's today's test results:
GH: 6 (I follow Diana's water hardening recipe to raise GH, KH of our NYC-area water though it seems I'm still a bit low on both)
So here's a fuller narrative to help the Hive Mind troubleshoot with us.
We used a local nursery's organic potting soil (ingredients of peat moss, Canadian sphaghnum moss, "forest products", and perlite). I did a full (nearly 10 days) mineralization process, which removed all the perlite. Because we live in an area with NYC's soft water, we did add in some dolomite and muriate of potash to the soil. And a very small amount (less than 1/4 lb) of clay for CEC (my wife is a potter, so we had that on hand). We used the Black Diamond Blasting stuff for the cap. The soil was kept at an inch and the cap at less than an inch.
We do not currently have a heater in the tank (our house stays 74-77 F in the summer), and just a very small HOB filter (the AZOO Mignon 60, which has a very low flow of 15 gph). We have had biofilm (on water surface) issues since week 3: I skim it daily, though I ran a gentle airstone, which removed the biofilm immediately, for a couple weeks as an experiment.
There is a (relatively) large piece of spiderwood driftwood in the tank but it was placed on a stone which was sitting on the glass. Though this may not have made any difference (see below).
The light is a 12 inch Finnex FugeRay Planted+. I can't seem to find published PAR values for the 12" size of this light anywhere, but the FugeRays are known to be fairly high so I built two sets of risers to put the light up off the tank (one set is 7 inches up, the other is 12 inches). I have had the tank on the "siesta" regimen (5 hours on, 4 hours off, 5 hours on) since day one, with no serious algae issues that I can see (just some usual start up diatoms) and now a bit of brown algae on the glass and the pennywort leaves.
We saw pearling on the plants the first two days and then none since. Plant growth has been poor. The amazon swords all melted away. The bacopa struggled with lots of die off until they acclimated and put out some small roots; they've since grown slightly. Dwarf Hairgrass has hung on but hasn't grown. The dwarf chain sword is similar. The tiny crypts largely died off, though that might be because it was tissue cultured and I stupidly planted it in clumps and in too shady of a location (under a driftwood shadow). Even Hornwort, which was doing okay (though the growing tips were brown) has been dying slowly and losing vigor since we added Pennywort and Salvinia. The Marsilea hirsuta (sp?), Trident Java Fern, and some Weeping Moss were the only plants that have really grown much at all. The exception is the Salvinia, which reproduced like crazy, but the new plants have TINY leaves and are very, very pale green. The Pennywort too has seen its leaves get smaller and very pale (almost white).
After the amazon swords melted, we added some vallisnerias and some medium sized crypts -- both of those melted a bit but now seem to have adjusted. At the same time we also added some new small leaved anubius that are doing okay -- one seems to be throwing out a new leaf here in the last few days.
I kept thinking the plant struggles were due to the light -- too much, too little, etc. So I've played around with the different heights a lot. None of it has made any noticeable difference. After stumbling on a thread here last week, I now suspect that maybe it's been nitrogen deficiency. Even after the tank was cycled, our nitrates were essentially zero or just trace all the time: we cycled the tank "fishless" and so were not adding in fish food. My hypothesis is that all the plants were just sucking all the nitrogen up and starving each other -- hence the small, pale growth on several of the species. I removed almost all of the Salvinia (in case it was the nitrogen hog) and did start adding small amounts of fish food every couple of days in the last week or so and perhaps that is responsible for some of the new growth I'm seeing (Anubias and Java ferns).
But even if I'm right about the cause of the lack of plant growth, the livestock deaths must have a different cause. Some more context:
Following advice in threads here, about a week or two into the tank, I began poking the substrate with a long piece of wire and sure enough I was releasing a LOT of hydrogen sulfide bubbles, particularly around the base of the driftwood. Those bubbles seemed to be inexhaustible -- every day I could release dozens or sometimes hundreds of them and the next day they would be back again just as bad. So, after the Amano shrimp debacle, I decided to pull the driftwood out. Wow! What a stink. That whole area just reeked. That discovery led to me tear down the tank: I scraped the cap off as carefully as I could and then removed the soil. About half of the soil smelled absolutely foul, particularly around the two rotting amazon sword root masses.
Not having any other soil on hand, the half of the soil that didn't smell so bad, I put back, in a much thinner layer, with a new and even thinner cap. (I did seed it with a handful or two of the old cap to help establish the bacteria colony.) And I replanted. The redone tank had a one day ammonia spike, but cycled (no ammonia, no nitrites) within 48 hours. Then we added the MTS, thinking they would keep the substrate aerated with their burrowing. They were seemingly fine for about a week (5-6 days) and managed to uproot almost all the Marsilea every few hours it seemed (so I removed most of it too), but now are all motionless for some 48 hours. Some of them are turned with the opening in their shell pointed up, and I fear the worst again.
So, I'm basically at a loss. I suspect the soil is the culprit but I can't see how or why it would have turned so toxic. Frustrated beyond words, in large part because without a plausible cause or explanation, I can't decide on what I should do now.
Do I just tough it out and give this yet more time to "stabilize"? Or, do I tear it all down and start over with new soil? And if so, which soil? (I'm leery of using using the same stuff that I mineralized and that seems to have gone toxic in case it has been contaminated with something.) I don't want to use my garden soil as it has a very high proportion of colloidal clay and the tank would not clear for months. Or do I just pack it in and go "high tech" with some commercial soil, CO2, and lots more maintenance effort (though to be honest, setting up this tank has already required many times more time, thought, and effort than I had thought it would).
EDIT: Since tearing everything out and redoing with only half the soil, I get no more bubbles of H2S, but I do know from some of Diana's posts in other threads that it can be dissolved in the water column and be leaching out of the substrate without ever forming bubbles. This is what I suspect is happening to my tank. If so, my question is why? My soil and cap are both thin (have been from the start) and the wood is resting on a rock (which is resting on the glass), hence there is no compaction of the soil happening there. Further, the Anubias and weeping moss and Java Ferns (all growing, perhaps the best of everything in the tank) are all attached to the wood, so if it was the source of the H2S one would think they would be suffering.
Pics for diagnostic purposes are below. (And I apologize for the length of this post.)
(my apologies for the red blob -- that's a reflection of my home depot water change bucket below and in front of the tank)