The second dose of Flub is still going (nearly over) in the main tank (and everything seems fine, which makes the following that much more baffling):
I decided to use the flub on the new arrivals in my QT tank, as recommended in wkndracer's QT thread above. The QT is a 10gal mostly-bare tank (has some colored-glass pebbles covering the bottom, a couple of fake plants, and some frogbit floating about) with a heater and Tetra internal filter (cycled media from another tank). In QT, I had five ~2" Rainbows (3 Bosemani, 2 Turquoise) that I've had for over a week and were doing excellently by every measure I have (great color, appetite, activity level, normal poop, etc). 50% WC's were done every 2-3 days, with ammonia staying consistently low (not quite zero on my continuous-indication meter, but well below the next increment of 0.05ppm). I was not testing nitrite or nitrate because of the frequency of the WC's and how well the fish were doing.
Last night I did a 90% WC (per the flub instructions) and dosed the flub into the tank (may have been slightly overdosed, but by a really tiny amount like a 9.5-10gal dose in ~9gal of water volume). Took a while to get the flub to dissolve, but it did.
Here's where it gets weird:
On my main tank, after the flub dissolves, the water is clear. After the flub dissolved in the QT, the water was cloudy.
By morning, the water was still cloudy, but the rainbows seemed ok (however, they didn't have much of an appetite when I fed them). Charlie's instructions for the flub say to have "live wiggling or jumping food" for the fish as they recover, so I suspected that flub might cause a loss in appetite and began to wonder if I was doing something wrong with dosing the main tank, not that something was wrong in the QT.
When I got home from work this evening, I noticed the Rainbows were swimming at the top of the still-cloudy water and got concerned. I was trying to figure out if I should abort the treatment and do a WC or if I had time to post a thread and ask about it.
45 minutes later, I saw two rainbows laying upside-down on the substrate and not moving. I immediately jumped to action by netting all 5 fish and putting them into a guppy tank nearby, but it was too late for the two on the bottom. BTW, they look completely fine, even had good coloration when they died. The other three are stressed, but seem to be bouncing back.
A closer look at the water shows that it's not just cloudy, but there are long white stringy filaments floating about and clinging to the outlet of the filter (you can see it hanging off the fake plant in the picture). It's almost like a fungus you'd see grow on food left at the bottom of the tank, but there's way too much of it and it's too long to have grown overnight. None of this stuff was in the tank when I did the WC last night!
The presence of the white-stuff and how dense the cloudiness is leads me to doubt that it's a bacterial bloom from the large WC (and the slight bloom I had when I started the QT was far less than this). UPDATE: I just did a test on the water and couldn't even detect a trace of nitrite.
What could this be?! If it's related to the flub, I'm going to be far more hesitant to use it in the future.
Last edited by FlyingShawn; 12-16-2011 at 06:37 AM.