I have some tap water sitting out so I can test it at 12 and 24 hours for pH and KH/GH however I haven’t really seen this issue of dropping pH until this week.
You are correct about the filter. It’s relatively small so it would have to be a very small bag of crushed coral to sit on it and allow water to flow through.
Cuttlebone fish is probably a more feasible choice. Since this tank would only hold a betta (and maybe a nerite snail in the future), just break up the cuttlebone and put very small piece in the substrate, and replace when dissolved?
You are correct about the filter. It’s relatively small so it would have to be a very small bag of crushed coral to sit on it and allow water to flow through.
Cuttlebone fish is probably a more feasible choice. Since this tank would only hold a betta (and maybe a nerite snail in the future), just break up the cuttlebone and put very small piece in the substrate, and replace when dissolved?