Undergravel Filter Flow Requirements

[Wastrel]

DIY is the way to go. You don't need PVC pipe. Plastic tubing works fine. You should get a large size for underneath the gravel and perforate it. For a large aquarium, you might need quite a few feet of it. You'll have to work this out: the ID (inside diameter) of the large tubing should be the same as the OD of the next size of tubing, and the ID of that should match the OD of standard tubing. This is to fit the tubing together. You don't need to glue it. Lay the large tubing down in a spiral, covering the bottom from the middle outwards. Get a T connector to hook up the air supply, the bottom tubing and the upright bubbling tubing, and Bob is your uncle. Put the gravel on there, at least a couple of inches deep.  No, you do not need a strong flow; a bubble or two every second is enough. You do not need an airstone, and they get plugged up anyway. I hope that's clear.

I have my bubbles coming up through a big pile of rocks at one end of the aquarium. These rocks average about 1" in diameter and they are expensive on Amazon for some reason. They are cheap from Dollar Tree. A big pile of rocks provides space for small crustaceans, worms and decomposing bacteria, as well as giving fish nooks and crannies to explore and find the occasional tasty morsel. Fish fry can hide there. Plants such as Java Moss also grow in and on the rocks.

Undergravel filters are environmentally sound. For a freshwater setup, you should really get a small amount of water from a creek (that is not very polluted, that can be hard to find, I know) and use it as a biological starter for your UGF. If you are more ambitious, get a fairly good amount of water and use a magnifying glass and an eyedropper, or a spoon, to collect copepods, amphipods, and ostracods to live in the aquarium. If you get those rocks, they will hide there and be a constant source of food. With regular water changes, the accumulation of crud in the gravel is not a concern, because it is broken down by micro-organisms and eventually comes out into the water.

Edited June 11, 2023 by Wastrel