Undergravel filter system

Question
QUESTION: I have a 50 gal. aquarium "wall" (14"Wx22"Hx60"L)with fluval canister filter beneath which intook from an undergravel grate as well as above gravel intake. I recently replaced with new, fine gravel and had a new undergravel filter pan installed but now when I brush down algae it just settles and doesn't get filtered out. I think the new gravel is too fine and acts as a barrier and that the pan has too fine intake holes. I can't find any information or source on other types of undergravel pans with larger holes. Any suggestions?

ANSWER: Hi Mary,
They generally dont make undergravel pans with larger holes because they clog extremely easily. Your best bet is to get a coarser, larger grain substrate and mix it with the old fine substrate you have. You can do it in sections in the system over a few days so as not to disturb the biological filter or your pets too much. It's very common for fine substrates to inhibit/limit the efficiency of an undergravel system. They do cause a barrier that only the tiniest of particles can get through. You can also power the undergravel system with power heads rather than the canister system for a few days once you mix in a different substrate to get it flowing properly. Then switch it back to the canister. Undergravel systems can be tricky to get going properly, but they are still an very effective filtration system. Very similar in concept to a Jaubert plenum system. So hang in there and get the substrate mixing going. You'll get it!

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QUESTION: Thanks. I'll try larger gravel. I see some called cichlid - is that what I should look for? Is there a desirable size measurement I should look for? Also what do you mean by using power heads rather than a canister system? I don't know what a power head is.  Thanks.

Answer
Hi Mary,
I would just look for crushed coral substrate, it comes in various sizes that will be perfect for what you are doing with the undergravel and canister filtration. It's designed for marine systems as well. A power head is a small water movement pump. Has a small inlet tube with a screen and and outlet. The inlet can be used in place of an air line and stone for the undergravel filter. It simply gets inserted into the undergravels up pipe below the surface of the water. This will increase flow through the substrate for a day or 2 once youve mixed in the larger sized substrate. If you dont have one it's not a necessity. It's just another option/suggestion to help get the undergravel sytem going. Once again, not a must.