What happened to my fish?

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Freezekougra

Feeder Fish
MFK Member
Feb 18, 2009
1,112
2
0
Brooklyn, NY
I've been neglecting my tank a bit, but I finally got around to doing a w/c after 2 or 3 weeks. W/c was 50%, added prime as usual....i haven't changed anything in my tank for months. And I've had the angelfish in there for nearly a year. Right after the w/c all my fish started swimming upside down and some laid on the substrate as if they were dead. I checked ammonia and it was 0, so I don't think there was ammonia building up from compact sand. ~30 mins later all the fish seem fine...but I really want to know what happened so it doesn't happen again. Was there something wrong with the tap....did I go too long inbetween water changes? Skipping 2-3 weeks for just one time doesn't seem lethal to fish.
 
my first thought is that since you were late on the water change, when you did do a water change you changed the water chemistry rapidly by %50 which fish don't like. It is the same as the need to acclimate fish to new tanks, because the water chemistry is different from tank to tank.

If it has been a while since your last water change do smaller water changes at a time. Instead of %50, do %20 one night and then another %20 and so on until you have your parameters in check. After that keep yourself on a weekly schedule, 50% weekly is fine so long as you have not missed a bunch of water changes.
 
Best way to know what to have checked the kh and ph of the tank and your tapwater (not ph, ph isn't imporant here). My guess is that you sent them into osmotic shock due to different levels of hardness between the tank and your tap.

Best way to ensure the hardness is the same between your tank and the water source is to do large and constant water changes.

OR, perhaps it was a temperature change?
 
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