Puzzled...

[Warnberg]

What would cause a 2 year old tank (240 gallons) to suddenly have a rise in nitrites and nitrates?

I pulled eggs from the clowns Thursday night and noticed one of my corals was loosing flesh from the tips. So after getting the eggs moved I tested the water (everything)

Ammonia 0
Nitrite ~ 2 ppm
Nitrate ~ 5 ppm
Calcium 420
Alk 8 dHK
Mag 1350
pH 8.3

I looked for anything dead and could find nothing. What could have caused this? Any ideas?

Needless to say I changed 40 gallons yesterday and am slated to change another 40 today.

[lcstorc]

Either something dying or excess food rotting are the only things i can think of. A dead snail perhaps. Sometimes it is hard to spot them.

[Woodstock]

A fast influx of organics causes a cycle to an established tank. Did you disturb the sand bed? Are any large corals/anemones dying? Did a young child dump in a lot of food?

[Warnberg]

Well that is what I though as well, but I've never seen this before and I know I've lost animals in there before without finding them and no issues. I figured with 240 gallons (~300 total volume) it would take something fairly large to cause a spike like that.

You know, I wonder.... about a week ago I was working on the pool in back and handled some chlorine tabs, about 4 hours later and several hand washes I fed the fish. You think there is any possible way I could have gotten a small amount of chlorine in the tank and that killed off some of my biological filter?

[Woodstock]

Highly likely!

[Warnberg]

I was afraid of that.... now the question is what to do to fix it... water changes, aeration (lots) and time I guess to fix it.

One other thing I caught, the tank's lights all went out and couldn't figure out why... well what I found was (thank you RK2) I set the lights to go off if tank temp hit 83 on the reefkeeper and what I found was the pump (mag 7) that feeds the chiller quit. So I replaced the pump and brought the temp back down to 80, it never got above 84 in the tank but I would bet the combination of the two caused the spike.

[Woodstock]

A high temp can cause a dieoff. I have my lights to shut off at a lower temp (81). You may want to lower yours too.

If your ammonia is 0 then you are past the worst part of the semi cycle but keep testing until both ammonia and nitrItes are zero. Perform water changes if the ammonia raises.

[Warnberg]

Well after worrying all night about it I tested again this AM, here are the results.

Ammonia 0
Nitrite 0
Nitrate ~2
alk 9.0 dHK
Calcium 380 (trying to raise this a little)
Mag 1400
pH 8.1
temp 79

So I'm going to do one more water change today (40 gallons) and keep an eye on things for a while. I did crank up the skimmer last night before bed and went aggressive skim with it. Lots of gunk this morning so am going to clean it and leave it aggressive for a few days as well.

[lcstorc]

Sounds like a good plan. Water changes and a good skimmer can fix a world of wrong.