My 75 gallon mystery.... :(

Modemagic

Modemagic

Premium Member
For the past few months I've had a pending 75 gallon mystery. Any new fish I put in my tank die. Never immediately, but in a few weeks of being added to the tank, dead! Been through two Yellow Tangs, a Bicolor Angel, Foxface Rabbit, 5 Chromis, Coral Beauty, and a Scooter Blenny that I recall. Tank setup is a 75RR tank with a trickle filter, no bioballs in the tank, and a skimmer in the filter. I do run carbon in the filter using a media sock and change the filter pad frequently. Lights run for 5 hours a day, but tank does have natural sunlight that is on the tank during the morning hours when the lights are off. Approximately 35-40 lbs. of LR in tank currently. Water changes done regularly as well.

NOTE: Not all of these fish were in the tank at the same time, nor added at the same time. Tests were performed before adding any new inhabitants to ensure levels were within acceptable range.

Levels are all in the acceptable range in the tank, testing for:

Ammonia
Nitrites
Nitrates
pH
Salinity
Alkinity
Calcium

I even have the guys at the fish store stumped on this one. Currently all I have left in the tank are two percula clowns which I've have for 10 months or so, a cleaner shrimp, a chocolate chip starfish, an urchin, and a variety of snails, and hermit crabs. No one seems to have an answer as to what keeps killing any new inhabitants to the tank.

Prior to any deaths in the tank, none of the fish seem to display any real signs of trouble. A few of the fish have hidden in the rocks for a day or so, breathing what seemed to be heavily, but have not seen this trait with all of them.

Anyone have any thoughts as to my mystery killer?
 
I bet it's ich. You mention it takes a few weeks. Even if you don't see any white spots, it can still be ich. I would leave the tank fishless for a month or more to let the ich run its course.
 
Wouldn't that have killed everything in the tank though? Can I dose the tank with something since I don't have any corals in the tank currently?
 
when i had the ick proplem all scaleless fish died tang ,coral beauty and scotter blenny you do have a uv light right?i didnt .have one now
 
Ich won't kill invertebrates, and any other fish may have simply been able to resist the parasites better than the others. Treating with copper based remedies will kill the invertebrates and all your LR.

The fishless method take patience, but it works.
 
I had a tank do this to me once. Killed any fish I put in. I finally figured out it was the food (mysis shrimp) I was feeding. Must have been rotten or something, as they ate it and then were dead the next morning. I even quaranteened them, but all were getting the same food. That is how I finally figured it out. Might be something to check out anyway.
 
Yeah, I doubt you'd see ick killing fish after fish without ever having seen any white spots. May have some other type of parasite, but I think I'd start with jimfed1's idea and change out the food completely (if you've been feeding food from the same source this whole time).
 
don't add any meds to any tank you want to eventually keep inverts in. Copper and other meds leach into rock and even glass.
 
The food is an interesting idea, but why wouldn't have knocked off my two clowns and shrimp? I've been feeding them a mix of frozen brine shrimp and 'New Life Spectrum Marine Fish Formula'. I do feed the New Life crap to my damsel in my 5 Gallon nano and the damsel in my 30 gallon tank, and they seem fine.

Here's a thought I had awhile back, far fetched as it is, but is it possible that my Urchin has something to do with this? I'm not to familiar with how aggressive they are, although I've never seen it try and go after anything, nor ever heard of such a thing.

Is it possible the fish, all bought from the same store are just crappy? I've considered road tripping to Coralville from Davenport to try a fish from SoM.
 
Last edited:
The urchin is not a threat to your fish, assuming it's the regular variety of urchin. They eat algae, plain and simple and are not aggressive towards fish.

I would get a good UV filter appropriate for your size tank and run the water through VERY SLOWLY so that any parasites and eggs, or larvae in the water column are eradicated. Do you treat the new fish that you've introduced with anything prior to putting them into this tank? Are they quarantined? Do you give them a freshwater dip? You should do one (if not both) of those things whne adding new fish. The clowns you have now may be immune to whatever it is that's causing the new fish to die........ hard to say, but generally clowns are fairly hardy.
 
I believe I have the answer to my problem. On a long shot suggested by one of my fish guys @ Aquatic, he suggested checking voltage in the tank.... 53VAC!!!

Holy Crap!

I only have three items in the tank, two heaters and the powerhead that drives the skimmer. Unplugging them all would drop it in steps, but never all the way down. So I went back to the store and picked up a grounding probe. dropped the probe in the water, plugged it in, and instantly dropped it to under 1 VAC.

To avoid further 'shocking' the fish, I am going to reduce the voltage in the tank slowing by unplugging devices over a period of time. Hopefully this should end my killing streak....
 
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