Yes, I run a canister filter, run carbon all the time, change it about once a month. Running an nitrate reducer in there now but can't remember what it's called off hand. It's a rechargeable packet like thing.

The powerheads have the sleeves. I wasn't running them and then ran them the last 2 water changes with brand new sleeves each time. They are now out again because my friend who owns the LFS said they can be a source too.

I'm pretty sensitive to the taste of heavy metals in water and I drink our tap water so I'm not sure that is a source.

Wow, this sucks, I feel your frustration! In my opinion you should ditch the canister. They are ok for fish only but personaly I would never use one on a reef system. Nitrate factory. Open a window or two and get some fresh air in, this will help raise your Ph some. I am thinking you may have too much bio-load for a 75gal. What with the population explosion of your snails and the 7-8 fish your filtration can't keep up. Also, invest in a RODI system, you may not be able to taste metals... but they are there. Hope some of this helps and good luck!!

I feel your pain as i'm going through the same thing.i'm losing my sps one after the other,i'm fighting a losing battle:cry: fish and inverts are all doing fine except for my corals...

Is there a way to test for heavy metals besides copper?

TDS meter for the tap water. Your pH is surprisingly low. What WarDog says actually made a lot of sense, your over consuming bioload from your snails may be a culprit. I had this actually happen in a planted tank with my fish dying off. I had a pond snail break out, and it got so overwhelming I couldn't keep up anymore (damn hermaphroditic snails) I found my tank went through another cycle just based off of the amount of bio load I had in the tank. I had about 70 fish in a 55g, with doubled filtration. Once my fish started dying off, I found that too much bioload was the culprit.

I ended up taking my entire tank down, cut all the leaves off, changed my substrate and replanted and moved my fish back into the tank and all was well after that - and I eventually, after several years - got rid of my snail problem. (Thanks to clown loaches, actually..)

Not saying that this is a direct cause, but it's a acute possibility.

I know you're not new to the hobby by any means, however; try perusing this forum thread: http://www.thereeftank.com/forums/f6...ed-160389.html - it might answer some questions you need answering.

I am a bit of a nube though.

I'm surprised it may be bioload though in a tank that has been stable for 3 years with the only addition of a file fish basically. I was wondering if my clean up crew starved actually. I have turbos, astrea, nassarius, urchin, conch, cleaner shrimp (now missing), coral banded shrimp, hermit crabs. I have been putting algae down on the bottom for them. As soon as a fish poops in my tank, it's a feeding frenzy. It doesn't even get to the bottom of the tank.

Could that die off alone cause the spike?

Wow, Neoh, that's quite the thread. One I could get lost in, for sure. Thank you for sharing it.

http://www.marinedepot.com/md_educationcenter.html

Here is an article on getting rid of dinos, scroll down to knowledge base.
I had an LPS die off a while back, never figured out why, I ended up fragging all the dead stuff and removing it and eventually it ran its course.
the ammonia is probably aggravating your situation, Amquil will detoxify the ammonia.

If you can get a hold of a bottle of Prime and also Stability from the lfs or a local reefer do so. Both assist in getting the bugs into turbo.
At peak time how many snails and hermits did you have in your tank.

i didnt see you post your salinity, double check your refractometer against a fellow reefers, or local store, fish can handle lower salinity, everything else suffers.... i see this all the time, someone thinks their refractometer is ok and it turns out to not be and that fixes everything

Steve