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Has anyone ran Harlequin rasboras at pH ] 7.0? With what result?

Welcome to FP!

What is the pH of your tank? Harlequins are hardy fish, and can adapt to different pH levels. As long as your pH isn't an extreme, you should be fine.

My tank is at 7.4 and the rasboras have been in there for 2 months.

Some of them did develop a case of cotton mouth\columnaris - not sure if it was from the stress of going from 7.0 at the LFS to my tank. But they all pulled thru and they're all fat and happy now.

I've had them in a pH of 8.5 with no signs of stress or illness.

They do well in slightly alkaline water. From what i have read their preference in nature is something like pH 5-6,5. But they are not real peat swamp blackwater fishes to my knowledge.

My pH has stabilized at 7.2. The rasboras seem not to have been affected by the 0.4 jump in pH. The pH increased along with the GH and KH after the addition of a CaCO3 rock. My platies and guppies seemed to be dispirited. The NH3/NH4+ and N03- were perfect and there was no apparent illness. Their behavior changed immediately after a second move. Then deteriorated once more after a third move. Not the treatment I wanted to give them but saw no other choice except to take them with me. I knew my dissolved salts and carbonate hardness were suboptimal for platies and guppies, according to a couple of different references. The LFS told me as long as the tank was stable and I kept an eye on it it might be worse to start playing with them when the fish were seemingly quite healthy. However, this was before the series of moves. The increased GH, KH and pH have affected the platies and guppies in some positive way. Their appetites and activity levels have increased, while the rasboras remain unchanged. Thanks to everyone for their input.

Does anyone has any thoughts on the importance of dissolved salts or KH? Experienced behavior change following GH or KH changes?