How to Find and Kill Evil Hitchhikers

[dunl]

If the only sign of damage was puffy gills, I say it's not an animal. I know of no animal that kills others leaving puffy gills as the only evidence.

[mark]

Your test kits current, checking for the usual (NH3, Nitrates), salinity, no stray currents, no temp swings?

Checking the tank in the middle of the night with a red lensed light?

[Pier Pressure]

I am using two different test kits for the ammonia/nitrite thing, one is just about brand new, and they are reading nothing. The highest reading of those I got was after I found the dead fish and shrimp and then nitrite and nitrate was 0.3 so just above trace. Since then nothing. Salinity, PH, everything exact same that night as it was the next day and remaining steady.

I have to pick up a red lensed light this weekend and check out some night viewing. Where would a person get one of those?

After staring at the tank tonight until I am just about blind, I know for sure I have at least one of those gross bristle worm things. Red, about two inches long. Kinda looks like a centipede.

I am going to try the old bottle capture trick tonight and see what I come up with.

dunl, what DOES cause puffy gills? Any ideas?

This is a great site. Lots of support and lots of interest. Thank you!

[Ruth]

With that many fish etc. dieing in that short of period of time I highly doubt that it is a predator hitchiker. Particularly since you say they had no other marks on them other than puffy gills.
A couple of possibilities come to my pea brain. Did you by any chance have a power outage or loose circulation for a period of time? Do you run a skimmer and perhaps shut it off overnight. The reason I ask is because when I had a breaker trip and lost circulation overnight in one of my tanks I lost 4 fish (out of 7) and it was from lack of oxygen in the water. For the most part the fish I lost were large however on very large one (my Naso Tang)survived. Some fish are way more suseptable to an oxygen drop.
The next thing to explore is water quality. I know you tested yours but could you please let us know what brand of test kit you are using and what your #'s for Ammonia, Nitrate, Nitrite, PH, calcium, alk/dkh, and magnesium are. Sometimes it can be an inbalance in chemestry however I do not suspect this in your case.
Of course the last thing is some kind of disease that only effected some of your livestock and that list is way too long and complicated to try and guess at.

[Okguy]

I normally just lurk in the background around here, but I thought I would put my 2 cents in on this one. I agree with Ruth.

Originally Posted by Ruth

With that many fish etc. dieing in that short of period of time I highly doubt that it is a predator hitchiker. Particularly since you say they had no other marks on them other than puffy gills.
A couple of possibilities come to my pea brain. Did you by any chance have a power outage or loose circulation for a period of time? Do you run a skimmer and perhaps shut it off overnight. The reason I ask is because when I had a breaker trip and lost circulation overnight in one of my tanks I lost 4 fish (out of 7) and it was from lack of oxygen in the water. Some fish are way more suseptable to an oxygen drop.

Clearly not enough carnage to be a killer hitchhiker. Believe me I've seen my fair share of them...

My feeling is that the bioload was just too high to maintain the oxygen level at night or the CO2 levels got too high. 6 fish in a 28 gallon is an extremely high. While you're able to maintain the water quality with weekly water changes the oxygen levels we're probably dangerously low at night as everything in the tank would be using the oxygen and nothing can be creating it (unless you have a refugium on a reverse photo period). Adding the new critters probably put you over the top. In an oxygen deprived enviroment the larger more advanced species usually go first (ie. the fish and the shrimp). Which would explain why the hermits, snails and corals survived. The firefish just got lucky and it would explain why he is now freaked out. I think I would be freaked out if I almost suffocated .

Good Luck!

Kevin