Fish keep disappearing

vithi · Apr 26, 2022

I need some help.
I have a 500 liter reef tank, mixed reef with basic corals and fish. No anemones.
The inhabitants are:

2 x clownfish
2 x bangai cardinal
2 x pyjama cardinal

1 x halloween hermit crab
1 x green emerald mithrax crab
1 x blood shrimp
various snails

Or rather.. that were my inhabitants. It started when I left for a 1 week ski trip and put on an auto feeder. When I returned I had algae starting, and my acropora was almost dead. I lost 1 Bangai. Couldn't find the body. Checked in tank (didn't remove rock though), overflow box, sump and behind the aquarium stand on the floor.

Then over the next few weeks/month, I lost my second Bangai. All of a sudden he's gone.

Now today I can't seem to find my second pyjama cardinal.
After my ski trip I started doing regular water changes of +- 15%.

My water values are, according to the last ICP test on the 13th of April:

I started with dry dead rock so predators shouldn't be an issue, but can't rule it out since I did buy some frags with a plug/stone attached (very small pieces, dipped everything).

Besides continuous algae (growing worse it seems), my corals have started to do better again. I just need to find out what is killing my fish.

Hope someone here can help!

Bucs20fan · Apr 26, 2022

Barring your parameters being way out of whack while you were gone. You could have had a bacteria bloom which depleted the oxygen in the tank, which cardinals would be especially susceptible to. The vanishing body could be because your clean up crew is doing and exceptional job. Just a thought. Was your water cloudy upon your return?

vithi · Apr 26, 2022

Bucs20fan said:
Barring your parameters being way out of whack while you were gone. You could have had a bacteria bloom which depleted the oxygen in the tank, which cardinals would be especially susceptible to. The vanishing body could be because your clean up crew is doing and exceptional job. Just a thought. Was your water cloudy upon your return?

Not cloudy. CUC could be doing great job, although it's pretty small for a 500 liter tank. Think I also lost a few snails, can't see many any more.

I do have a Deltec 1000i skimmer, 2 Vortech MP40s, 1 Vectra and 2 Radion lights. My return outlets are pointed toward the bottom of the tank. Do you think I should add a small wave pump to increase aeriation?