librarygirl
Look It Up
It's very small, river rock looking stuff, natural color. I put some in a dish with vinegar and nothing happened. So maybe it it just the water. Does high pH and hardness make it hard for fish to breathe?
I'm not sure. I'd take the Top Fin out if you can. Your PH is fine at 7.8. The 8.3 would be OK too as long as it's stable but larger water change could be a bit tricky due to the difference in PH from the tank. I'm not a PH expert though. Maybe Eco23 will find his way here and reply; or you could send him a private message and see what he thinks.