Here we go again: MIs, Take III

[Samw]

Originally Posted by Aquattro

The other guy here that got two had them eating everything in 2 days, fed multiple times per day. They lasted a week. He says he has strong flow and doesn't drop it at night, but woke up to 2 dead fish one morning.
Based on that, I'm going to wait a while before I relax a bit

Again, died overnight. Both at the same time. DO level is always at its lowest at night when lights out after several hours. As I said before, strong flow does not equal high DO. This has been measured before in Eric's paper and also I had strong flow at the surface of my tank which didn't really increase DO. Obviously, I don't know the setup and am just speculating, but the only way to know for sure what the DO levels are from 2am-6am is with a DO monitor/meter which almost no one uses. The sudden death overnight of both animals is a clue. Why always at night? If diet was an issue, the fish would waste away slowly. We've all seen what it looks like when a fish dies from malnutrition.

DO levels fluctuate wildly from day to day, night to night. But the lowest levels are always at night after lights out for several hours and the levels each night are different. I've had my levels go from 125% saturation during the day to something like 35% at night even with skimmer on. Some nights I get 40%. This was 10 years ago. Nowadays, I think I'm getting closer to 80% at night since I have no algae and deploy a UV sterilizer. There are countless things that affect DO but very few aquarists know what their lowest DO levels are at night. In most cases it doesn't matter because many big systems have enough DO for almost all of the fishes out there. Most marine fishes don't need a lot of DO. I think clownfishes only need 18% DO. I read that just a while ago.