Mysterious fish death

[Jkmjkm1198]

I have a 20 long reef tank drilled out with a 10 gallon sump, system has been up and running for about 5 months with no issues, the original stocking was 3 yellow staghorn damsels, one traditional ocellaris clownfish, one starry night blenny, and one tomini (flamefin tang). Everything was running smoothly for 4 months, started with the 3 damsels to cycle, and once parameters were stable I moved the clownfish and the blenny in from my old tank. I purchased the tomini tang as a last resort to try to control a hair algae outbreak. Within the past month the fish started dropping, it started with the starry night, it ate before I left for work and when I came home it was dead, same with the tomini tang the next day, and the third day the clownfish. I assumed the damsels were going on a rampage and killing the fish, so I tore down the tank and moved them into my 75 gallon tank. I purchased a yellow clown goby and a blue head pink damsel to try to start new (my corals and inverts were never effected and my water parameters were still stable) and after a week I purchased a juvenile orange shoulder tang to grow out to eventually move to my 75 gallon, then the fish started disappearing again, the first the damsel, then the clown goby, then the tang. I'm running out of options, I have more than enough biological media than I should need (about 3 gallons worth of ceramic media) and throughout this my water parameters have been stable and weekly 20% water changes have been done. Ive asked my LFS if they have any ideas but theyre unsure of what it could be, I'm running out of ideas/solutions and I don't want to keep buying fish and having them disappear.

 

[leedsrhinojohn]

Have you used any chemicals? things like deodarent, air fresheners, scented candles, anything like that at all.
Have you put your hands in the tank after just spraying something or washing something.
Anything like that is a common cause of mysterious fish deaths and stable water parameters.

 

[Jkmjkm1198]

No, Im always careful with stuff like that, only using spray stuff in other rooms, etc. Ive been around and maintaining fish tanks all my life, I just cant seem to keep anything alive in this tank

 

[leedsrhinojohn]

You might never know the cause, its just one of those things you hear quite often but never find an answer to.
I would look at anything at all you have done differently, used different equipment, added something different or taken away something different.
Have you checked your ro system, such as filters, is the di resin ok, has it been anywhere near chemicals of any sort, is the room where you mix your water safe, is the bucket you mix in safe.
Just go through every little thing you can think of regarding your tank.
Certainly do not waste money on buying anymore fish until the reason is pinned down.

 

[vetteguy53081]

Check also for stray voltage and even too high/low salinity. If you’re getting false readings- that will do it. Perhaps take a water sample to a trusted Lfs and have them test and see what they come up with and to compare with Your test results

 

[Jkmjkm1198]

Ro/di unit is maintained regularly, I use an empty salt bucket to mix the water in, and theres nothing in my room that would be hazardous. It's stumped me, and the owner of my lfs (good friend of mine had him come check it out before posting). Nothing has changed equipment wise fish just started dropping out of the blue.

 

[leedsrhinojohn]

Good shout on the stray voltage, well worth checking.

 

[little_sardines]

When you say your fish are dropping - you're finding bodies? or are they just disappearing?