I've had my small system (8-10 gal) for a few months, my Ph is 7.6 and 9 drops for KH to turn yellow. I've had one catfish in it since the start, and just added some Koi. After one day, they are still quite skittish, so hopefully will settle down. But, the issue I'm concerned with is a white film that has developed over the top of most of the media. It comes off easy, but it comes back quite quickly too. Guessing something is out of balance. Any thoughts?
Here is a picture of the system with the white on the rocks
Don't sweat it...it's just mineral efflorescence from your source water. That's super common to see...it's mostly calcium precipitates, and tastes pretty chalky.
Thanks for the help!