Sudden unexplained deaths

[KayJay]

Hi members,

I'm new to this but at my wits end. (Sorry for the long post)

6 x 2 x 2 fowlr tank
2 x 1 x 1 sump
Protein skimmer
Powerheads x 2
Tank running for approx 7 months
Fish in it for 4 months
5 ocellaris + 2 barrier reef chromis added first
1 month later + lipstick tang + foxface + valentini puffer (got stuck behind the back wall 3 weeks later )
1 month later + empires angel (adult) - died 3 days later of bacterial infection
2 weeks later + flame + bicolor + emporer angel (all jeuveniles) added more live rock and purchased more salt (different brand)

Each time I purchase fish I take a water sample to lfs for them to test before I purchase and I purchase more clean up crew. Currently have 4 variety starfish and a variety of snails.

All my water tests have always been spot on.

All fish have been happy and feeding.

3 days after last fish purchase I lost 2 angels. The next day I lost the bicolor and one if the chromis. I took both these to lfs and there wasn't a mark on them, their gills were fine and they were brightly coloured. lfs scratching his head as water test was still fine (kh a little low but nothing a teaspoon of bicarb didn't fix). I sent a water sample to Triton and waited. Lost all fish except the foxface over the ensuing days. All with the same symptoms....none! Feeding and swimming happily one minute... dead an hour later. All clean-up crew are still alive and I even have baby snails.

After 3 weeks Triton results are in.... high levels of tin 2.156 and toxic levels of zinc 59ug/l. All other reaults were ok.

So.... did the zinc kill my fish?
...where has it come from?
....how do I remove it?
.... how can I regularly test for it myself without having to go back to Triton?

On the advice from my lfs I have checked my tank and sump for anything metal. I have two stainless steel clips that are outside the water. My algae scraper is plastic. I do have a magnetic cleaner that has been in the tank the whole time (removed now though)

I'd really appreciate anyone's advice, suggestions, experiences.... anything. I'm sooo upset.

KayJay

[Ageofaquariums]

What water do you use for water changes and what water do you use for top ups? I have only seen this problem with very new houses tap water and old houses rainwater. Even heavy metal doesnt usually cause sudden deaths like that tho.... any chance you have a mantis?

[KayJay]

Hi AoA,
I use RODI for tops ups and Salted RODI for water changes. I make the RODI water myself. Our house is 14 years old....not new and not rainwater.
No I don't have a Mantis.
Any other ideas then if it's not the zinc levels? My daughter thinks my foxface has killed them all hahaha
Cheers

[colg]

Can you post up some of your param's?
Temp, salinity, N02, Ammonia, etc.
Having a skimmer should provide enough oxygen exchange but its worth checking (however your fish would be pretty high in the water column and you would have mentioned this).
Maybe running some carbon would help remove pollutants that haven't come up in the Triton test.