Is it harmful for there to be a build-up of tiny particles on the bottom of tanks? They just look like small flakes, I'm guessing remnants of food. They seem to settle on the bottom and so they don't get sucked up by the filter unless I'm changing the water, which I do weekly (50% change) - and even then, they settle too fast to be filtered out.
As for my setup, I have a 20 gallon tank for two yearlings with the Finnex PX-360 canister filter. I realize that this filter may be inadequate based on the size of the tank, and the tank itself might be small for them, but I'm just wondering if this is a normal issue even with a bigger tank size and better filtration, or if the tank should typically remain clear of those particles. I suppose feeding them outside is an option but I'd like to avoid that if possible because I have limited space.
On a somewhat related note, how often should I be cleaning/changing my filter?