Last monday, I got 3 corydoras julii (1 inch)and placed them in my disinfected 10
gal Q tank with a few squirts of BioSpira to accelerate the cycle. I've been feeding them three times a week with one sinking pellet and I've been changing the water every other day (40%).
After a week, the cories looked great, so I got three albino corydoras (3/4 inch) and three oto cats (1 inch) and added them to the Q-tank after a lengthy acclimatization period. I threw in an algae wafer for the otos.
Two days later, I noticed one of the juliis and one of the otos were dead. Another oto is MIA. The other fish seem fine. I checked my water params and was shocked to find 1.5
ppm NH3!! Nitrite and nitrate were 0; pH was 7.0. I immediately did a 50% water change.
I guess I got lazy for not checking the water params every day in an uncycled Q-tank.

I feel really bad about losing the cory.

Hopefully, the others will be OK.
I plan to cut down the feedings to once a week ( a sinking pellet for the cories, and 1/2 algae wafer for the oto), do daily 10% water changes, and check the water params daily.
Note to self

: Check water parameters and do water changes daily in uncycled tanks. Tank is cycled when ammonia and nitrite read 0 for five consecutive days. Thereafter, check water parameters with each weekly water change. Oh, yeah, don't try to extrapolate cycling experience with big tank to subsequent cycles...it doesn't work!