Dead Fish

Question
Hi Glenn,

Had a disaster over the weekend with all my fish dying after 2 months of enjoyment. I am very regular with water changes and checking acid and other chemical levels. For weeks the PH (8.2) Nitrate/Nitrite/Ammonia have all been 0 or .1. salt fine and temp fine. All fish eating well and getting along. 15Kg's of live rock (in tank 2 months before fish) 3 Chromis, 1 Tang, 1 Koran Angel and 2 Clownfish in 220 litre tank. The only thing I (or local store owners) can come up with was the skimmer. Since installing 2 months ago had many problems in getting running and finally got new pump last week which worked straight away. The possible problem was that the skimmer was only turned on for testing over the last 2 months so any water in the reservoir was only pumped back into tank in small amounts. When it finally got replaced I turned it on and it worked fine. 36 hours later all fish dead and milky cloudy water. I tested everything and the water was still perfect - no Nitrate/Nitrite/ammonia/phosphates/chlorine PH 8.1. I have tested another 3 times since with same results. Could the water that has been in the skimmer tank become polluted? Why wouldn't that show up in any test that I have done immediately? The only other new thing i did was put in some dried seaweed (preservative free - or so the packet told me) in between the rocks for the tang. If the tests didn't show anything and the fish died, what is to stop the next fish dying if there is something I can't test for? Very confused....

Answer
Hey David,
Sorry for your loss...
Rule out the seaweed unless it's WAY beyond its shelf life. If the water clouded, and a milky(white) cloudiness, it's generally either a bacterial bloom, a carbonate or phosphate spike, a nitrite spike or an ammonia spike. It can be caused by other factors but they generally dont cause fatalities. Did you check temperature? This can also be a factor in response to toxins with our aquatic pets.
How long did the water sit in the skimmer chamber/tank? It would have to have extremely high levels of ammonia or nitrite to do this damage. It is possible however, but it would show up in tests. Unless the tests were many hours or the next day after the spike. I have seen such spikes from malfunctioning canister filters before. They send a high dose of toxic water that shocks and kills fish, but is diluted within hours by the systems water volume. It's also possible that there was simply something from manufacture in the pump. Did you rinse and run the pump before placing it in the system? Alot of variables here. Has the cloudiness cleared up?
I would just test the water daily for a week(check your test kits as well, make sure they arent beyond expiration), check the skimmer daily as well. After a week to 2 weeks if no signs through tests and no cloudiness, I think it's safe to assume it was just one of those freak accidents. They do unfortunately happen. Especially with new systems. I know it doesnt help or make the loss any better, but they do happen in the early stages of a system that just hasnt matured and stabilized. Dont give up. We have all been there at one time or another. Let me know if you have any more details or info, I would be glad to help pinpoint any problems to help insure that it doesnt repeat. Do let me know how it goes.