Hi all, I am having an issue stocking my initial group of Sterbai Corys for my new tank. This is a 29 gallon, fully cycled, planted tank with gravel and two pieces of driftwood. I've been testing every day with a master kit (to make sure I'm not overstocking too quickly and such). Ammonia 0, Nitrite 0, Nitrate at 10-20 (up to 40 before a 30% water change). pH is 7.5, very soft water (I forget the numbers from the utility but if I remember correctly it was about 2 on the hardness scale).
I initially planned to start with my school of Lemon Tetra but the lfs was out of them so I decided to start with the Corys. I purchased 3 to begin, spent the hour acclimating them by temp, then 15 minute intervals of adding my own tank's water to their container. Added the fish and they have done very well, exploring, zipping around, parking under the wood. I monitored the water levels and after 6 days of no change (except nitrates) I did a 30 % water change and got 3 more Corys to complete the set. Did the same method of acclimation and one died within an hour, the other two within 8 hours. Original 3 (I assume) still acting fine.
I thought perhaps the stress of the trip and new tank had been too much, took them back and got 3 more. Two of them died within 2 hours and the 3rd seems to be acting as happy as the original 3. Total of 4 still alive and apparently happy (not acting oddly as far as I can tell from reading up on Cory behavior). Tank parameters still good this morning, no ammonia, no nitrite.
The only thing I can think is that the lfs says they keep their pH at 6.8 and mine is around 7.5 and it's too much of a change even taking time to acclimate them.
I'd love to have 6 to have a happy group, but my budget for fish is going to get pretty stretched if I have to buy multiple fish to find one that can adapt to my tank.
Any thoughts would be appreciated.