disease or not disease, that is the question

[choirboy]

I bought 3 yellow tail damsels. I have been have lots of problems with my 5 month old fish only tank so they are/were the only fish I had these last few weeks. One died in a couple of days, another a couple days later. The third is healthy as can be 3 weeks later. He is too small (3/4") and too young to have killed the other two, and I never saw any aggression at all between the 3.

I thought maybe there is some kind of disease killing my fishes? but they showed NO SIGNS of anything that I could tell. No spots (not even tiny tiny white ones), no isopods hanging on them, no funny behavior that I could tell (until right at the end)

Can I have ick, or velvet or something in my tank and just never see any signs of it in the tank or on my fish? And if I do have something in my tank, wouldn't it kill the 3rd damsel?

 

[MrTuskfish]

What are your water parameters, especially ammonia?

 

[choirboy]

they are as solid as a rock. I test twice each week. Once with ap tests, and once with salifert tests. I have both complete sets. I do this because A. they are a little hard/subjective to read, and B. I don't think they are ALL THAT in terms of accuracy.

For the last 3 months my numbers barely vary.

temp = 78
ph = 8.2
ammonia = 0
nitrate = <15
alk = 8 - 10
calc = 420 - 450
phos = <.003
sg = 1.023 - 1.024 (fish only tank)
only ro/di water ever.... with tds always at 0.00
water mixed for 24 hours before wc
water changes every 10 days of 10% (NEVER miss one)

Does that help? I am stumped. First tank in my longtime fishkeeping hobby that has been freaked out. x$##x

 

[hollister]

They didn't act funny ? like heavy breathing?

 

[Dr. Reef]

are u checking for salinity shock? most fish stores keep their salinity low at 1.016-18 levels and without proper acclimation fish cant handle the stress of salinity swing.

 

[choirboy]

Well, I don't check the lfs sg but I do take about 40 minutes to acclimate. Float bag for 10 min, then pour out 1/2, then add about 4 oz of tank water every 5 to 10 min for another 30 to 40 min, usually keep lights out during and for the next day.

The one sort of questionable thing I do (can't figure a better way) is at the end, I pour the bag into a net to catch the fish and then put them in the tank. It is a pretty soft net, but I still don't like to do it.

 

[MrTuskfish]

If its 3 damsels from the same LFS, the LFS could be the source of something. Most damsels are good at reducing their own numbert too.

This won't help now, but eventually not using a QT will catch up with you.