Mini Brittle Star Mass Die Off

[Delphinus]

I don't know if it's the cause but 1.028 is way too high. That's something I've never really understood. Mg obviously affects SG but so do a lot of things so 1.025 from a salt mix and then whatever Mg added to bring Mg in check to that brings up SG, but if it was say 1.025 plus Mg to get 1.028 is that equivalent to simply mixing more salt to get 1.028? More than likely not. So I can't even speculate if that's the cause here. Maybe??

The few things I can think of on top of what you have already looked for:

- copper (take a sample to an LFS maybe and ask them to do it)
- temperature swing
- O2 deprivation (likely not -- usually fish will go first if that were the case -- but, something to think about nonetheless)
- some other kind of toxicity to the tank. Detergent, soap, ..

Or it could just be a small enough ammonia cycle and the test kit just didn't catch it (it happens)..

Good luck sorting it out!!