I don't think fish rubbing and darting into the gravel is "normal" for them, I've only had fish do this when they're relatively new purchase not knowing where they came from and condition. I just did a tank with 14 mixed small african cichlids, tank has been established/cycled for years using two canisters.
Just about all of them are rubbing occasionally on the gravel, I'm also thinking they do this in the beginning stages of ich?
I figure I'd get all the fish I wanted at once, treat them (if need be) and let them grow.
So far I had them for about a week and I'm doing daily small partial water changes with the temperature set at 80-82f feeding them well, this has worked well for me in the past for most common fish diseases including ich without having to use meds.
After a few weeks I reduce the temp back to around 76F.
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