Woke up with things dead! Causes?

IDK either. I got the pump working again and within 90mins all surviving fish looked much better. Swimming around the tank like nothing happened.

 

what's your ph now?

 

I think I figured out the problem.

My heater is in the fuge. When the maxi-jet went out that would mean the heater would also not be able to heat the display tank. Even though we are in Florida the temp does drop pretty good over night this time of year. I never looked at the thermometer when i was checking everything, but I assume if the air temp in the house is 71 then the tank temp could have dropped far from 79 over night.

When the two fish and two shrimp died it could have lowered the PH. I don't really know if dying things and PH swings are a cause and effect, but if Ms. Corailline says it is, then it is. The PH may have swung, but the ammonia wouldn't have because I removed them fairly quickly from the tank. Probably within an hour of them dieing.

The only thing I can't figure out is how the brittle star made it. I always thought they were in the category of shrimp when it comes to hardiness.

 

Sorry for the losses

 

Another possibility for sure,but it sounds that you have it remedied either way with getting your fuge back online.Sorry for the losses.

 

Just a clarification:

When something dies it begins to break down immediately causing ammonia which is an acid. Acids will drop your pH the longer the decay the bigger the pH drop. Add to that a decreased available O2 from the pump off line and the pH takes another drop.

I believe you found a the contributing factors that lead to the issue, that is the most important thing.