what size undegravel filter do i need for a 20 gall?

Answer 1

I strongly advise against getting a UGF (undergravel filter). The idea is that is pulls all the gunk, food, fish poop etc into the gravel where it biodegrades. It's a good idea, but in practice, fish produce more waste than a UGF system can cope with. This will eventually result in a bacterial bloom that will cloud your water and/or kill your fish.

You can get away wiith it if you really understock your tank, but it's just better go with a hang off the back bio filter.

Answer 2

Don't get an undergravel filter. They work great- for awhile. Then they become a stagnant mess. All the goop that you're "filtering" gets stuck in the substrate, it never gets filtered out (think how you'd feel if all your garbage never got taken out of your house- tolerable for awhile, but soon it would just be gross and unhealthy).

You'd have to tear the entire tank apart to clean it, and then all your cycling would start over again. This is really stressful and unhealthy for your fish. Get a hang-on filter and make sure you clean it frequently if you really care about keeping the fish healthy.

Answer 3

As its name implies the filter uses your gravel as the filter medium to contain the bacteria that cleans the pollutants from the tank water.

Therefore the bigger the filter plate the more surface area of gravel will be acting as the filter. i would suggest that you get one that covers the bottom of the tank, thus maximising the whole of the gravel. In larger tanks it is worth having 2 uplift pipes, one in each back corner to allow maximum water flow.

However the best way to use them is backwards (known as reverse flow) rather than using a trickle bar at the top of the tank, stick the outlet pipe down the uplift pipe so that the water returning to the tank comes up through the gravel (a neat way of not having to clean the gravel quite so often and a great bacterial bed). this only works with gravel as aquarium sand is too fine and you will find the water disturbs the sand.

Answer 4

While the UG filter is tried and true, there are much better filters now.

I would recommend that you go with an external power filter, and I feel that the penguin line of filters is perfect for a 20 gallon tank.

Answer 5

dude, the gravel filter in the pet stores say which ones they are for like "Undergravel Filter, 10 gallons" or something, dont worry, if you cant find it, ask the people in the pet stores, they have to tell you anyway.