I changed it all. 3/4 cup new. Reactors are great. No sense in changing only part.

The sixline is now acting like nothing happened at all! Crazy.

Still appears to be the anthias and unfound firefish.

My Anthias has done weirder things before. Here's hoping.

SO AM I!!! Haha!

Thanks for the quick responses everyone.

Appears crisis averted. But still remains the question... WTF?!?!

Wow, weird. So, I didn't quite understand, in the end did none of the fish die, just sort of pass out? Or did you suffer losses here.

I'm thinking in a sort of "unexplained" tank crash or near-miss, it might be a combination of variables that just happened to line up. Like, probably, it WAS a low O2 issue, but exacerbated by a spawn earlier. I had a clam spawn once do a darn near tank wipeout, just all of a sudden fish started dropping out of the sky - there was no indication in the tank although the sump turned out to be a mess of goo everywhere.

Also had a large H. magnifica anemone for close to a decade - thing was huge - if he so much as burped or got ticked off for any reason, fish would die. In fact it was the tank wipeouts that pushed me over the edge with that thing and I got rid of it. Sadly, it died a month after being sold because it cratered the buyers tank. :( Such a shame it had to end that way. That thing would spawn too from time to time and man what a mess it would make.

You think about the things that can spawn in your tank - urchins, snails, corals, even fish sometimes .. it can put an unpredictable load on your tank out of the blue and for the most part it just filters out and may just be perceived as a slight bump in nitrates that even them in the end just disappear a week or so later - but then you add the proverbial straw to the camel's back by turning off all flow for 20 minutes and poof, it's just enough to push things over the edge.

Not saying for sure this specifically was it, but it could be just an unfortunate lining up of 2 or more variables at the wrong time.

I'm not sure I would be turning off my sump return when I feed, I've never done this myself as I don't like the idea. I do however turn off all the controllable streams when I feed. My two tanks are fed off the same wavemaker, my FOWLR does in fact go silent other than the sump return, but my big reef has a 6065 or something (I forget the model, a smallish noncontrollable stream) that stays on near the surface. This has the added benefit that food added gets immediately dispersed the length of the tank which gives the smaller or less aggressive fish a better chance of getting a fair share of feed - otherwise the bigger faster fish get the lion's share.

Anyhow something to consider, if I were you, I'd keep the sump return on when feeding, especially if it's going to be longer than 5 minutes for quiet time.

Good luck and sorry for your stress. There's always something in this hobby..

Leaving the sump return running would filter out the food.

I target feed so pumps off is necessary for a short period.

Once target is done I run power heads in tank.

The sump has constant flow due to two reactors on separate pumps so any issues with sump are non existent.

Crazy.

Re the stray voltage.... You might want to disconnect your ground probe and test with a multi meter just to be sure. Depending on where stray voltage might originate and the location of your ground probe, maybe some part of your tank was still affected, and some fish swam through that area.

Just a far fetched theory..., but might we worth another check.

Hey Pat,

We chatted earlier today about this... sorry to hear it happened but glad no-one was lost!

Chris

Could it be some chimical war from a coral or anemone? you cut off the pump and restart it, the coral or anemone get upset, released toxine in the water and that upset the fish?

If your fish were not breathing fast we can exclude lack of oxygen. That does not leave much? Can it be also some gas pocket from the sand, when the pumps restarted it released some gas in the tank just enough to upset the fish?

I would definitly put some fresh carbon.

Daniella, it happened while the pumps were off, not after they came back on.

food gone bad or something maybe??? assuming all were alive before the feeding the corals happened??