I have a 5 gal bucket that I use to mix the declorinator and tap water, then add it to the tank.
None of my fish seem to stressed about it. The bettas really seem to enjoy it.
Sorry about your oto as well, they are not easy fish to catch. I would try leaving them in during the next water change, and see how it goes.
Why must Gabriel nip at every veggie clip I put in the tank? I understand the bright clown fish one, but the new one is CLEAR. Anyway, I hope the Otos can get over there and snack on their zucchini.
All of them seem to be doing well still; they all have big bellies so I know they are either getting enough algae and/or zucchini.