Dead Fish

[RTRJR]

Nematodes are ubiquitous. Most are soil dwellers, free-living, non-parasitic creatures. Some are parasitic or injurious to certain plants or animals, but as in most large classes of organisms, most are harmless to useful. I add "beneficial" nematodes to bearded Iris beds every few years, as they destroy Iris borers and protect the plants from such.

Nematode population explosions in tanks are generally the result of excessive organic matter build-up over time, especially in the substrate (their normal home, where the feed on microbes which in turn feed on organics). The situation in a tank such as the topic of this thread is quite different - the sudden and serious anoxia forced them out of the substrate in seeking oxygen. You were likely seeing only normal populations in an abnormal place due to the abnormal situation. Most of us seriously underestimate the scale of the unseen infusorian populations in our tanks.

Seriously under-maintained substrates do develop enlarged nematode populations, and the minority of that excess is driven to life in water column, may even build up a visible line at the water meniscus (another rich feeding ground). That could be described as a filthy tank -as per the LFS - but most of those tanks do not look it. They are unlikely to show the typical signs ol OTS (old tank syndrome) and actually are not usually suffering from such. They are not really that filthy, just have excessive organics in the substrate and in the water column. More and larger partials without substrate cleaning would help but not clear the issue there.

They can occur even in densely planted tank if there has been no periodic refreshing (vacuuming) of the substrate when this or tank stand of plants is thinned and replanted. Many planted tank folk do not keep setups going long enough for it to be an issue. Those of us do keep setups long term generally do learn that if we do not clean the substrate when redoing this or that stand of plants, eventually the nematodes will appear in the water column (without anoxia). They are harmless and some fish relish them, but they are heavy hints (when commonly visible in the tank) that we could and should operate it with lowered organics.

HTH

[kerokero]

Pardon me for - yet again - being amused at another parallel with frogs. Recently in an effort to enrich the "ecosystem" in a complex soil substrate tropical frog tank, some keepers have been making sure that nematodes make it into the system. This in turn has freaked out a number of keepers that think of them only as parasites and in no way beneficial. A lot of keepers tend to think of their tanks as "clean" when in reality they are thinking of sterile conditions, then are horrified to find it not so sterile. I personally don't mind (but then I've studied ecology...) a few extras that do their thing, act as a gauge on the system, and occassionally are food for my frogs/fish, but then again I'm also known for my "grundge" methods Nematodes? Springtails? Pffffft. Good stuff

[dSerk]

Nematode population explosions in tanks are generally the result of excessive organic matter build-up over time

I started out with unmineralized peat/potting soil under the gravel AND I overfeed, so no doubt there's a ton of stuff waiting to be decomposed. I guess I don't REALLY need to overfeed if I'm fertilizing the plants, but I had a lot of bottom feeders, and, well, it's a bit disconcerting when you don't SEE your fish eat. So I overfeed.

I'd never seen them before, and since the tank has regained its balance, I haven't seen them again.

Thanks for the comments, yall. Next post will be good news only (or maybe a question or two). No. More. Disasters.

[kerokero]

But we learn so much from disasters! Ok, maybe it shouldn't be your turn then.