no more than 10ppm nitrate, you say? Ive got a planted tank that usually has 10-30ppm nitrate... Mine seem perfectly healthy, the females are saddling (I got them as tiny babies) and some are even holding eggs currently. None have died so far, except the two that got sucked into the filter (oops).
I tend to think the fish and such are much more adaptable to nitrates than is commonly stated. Not to say a clean aquarium shouldn't be kept, but honestly, does nature really keep below 10ppm of nitrate in streams and lakes?
Yes it does, actually.
Back when I caught some crayfish locally in a lake (man-made reservoir really, but they call them 'lakes' around here), I tested the water in the bucket and it came up with no traceable nitrAtes to speak of.
I certainly would not have expected that... I just remember hearing about certain recreation areas being closed due to the lack of good water quality... but come to think of it, that area -is- populated by people, not just animals. hmm.. I wonder why my nitrates are always so high then. no dead animals, 30% weekly changes, plenty of plants to eat it all up... odd. Thankfully though I haven't lost any of my fish/shrimp.
Nitrates will vary by location in nature, I'm pretty sure. Some fish will tolerate nitrates better than others. Cherry shrimp will tolerate higher nitrates, but reproduction/lifespan will probably be reduced. Shrimp in general are less tolerant of nitrates/nitrites/ammonia than fish.
I had a happy, fat shrimp for many months until I had an exterminator into the house. They all died, and new ones all croak shortly after being introduced to the tank (I find their little bodies). I've tested water, and had LFS confirm my results-- water is in good shape. Tank is 30 gal lightly planted peaceful community. I have done a number of partial water changes since the exterminator's visit, and have tried with RCS from several LFS's, but same result.
Two Q's, I guess:
1) Any guess why shrimp are dying?
2) Suggestions for how to remedy so I can once again have shrimp tidying my tank?
sounds to me like you have pesticides in your water..no LFS is going to test for that. tear down the tank..clean it..replace gravel, and decorations, clean filter replace media and try again..maybe go with ghost shrimp as testers since they are cheaper.
edit: Well if the gravel is epoxy coated you may be safe just cleaning it...but I would highly recommend replacing it.