QUESTION

hello and welcome to the board.

using an under gravel filter and an external filter at the same time is no problem at all. But, in my opinion, because i have used them, under gravel filters are a complete pain to manage and maintain. I would suggest using only the Penguin external filter or some other combination of filters.

good luck!!!
-chris

ps. no need for the all caps, we can read it just fine

I disagree. As long as you are doing your regular maintenance (including vacuuming the gravel) an UGF works very well. However, you will run into problems if you slack on the maintenance.

I say go for it.

A little trick to make the whole system run better is to block off all but one of the riser tubes on the UG, and install a riser tube that extends above the surface of the water. Stick the intake tube from the Penguin down the tube and now the Penguin is pulling ALOT more water through the gravel than any air pump, and you don't need to spend extra on a powerhead.

^good idea

then you have a direct link from the main bio filtration to the mechanical.

That is a great idea, my dad is persistant on having his UG filter running even though I am using 2 powerheads to pump a external canister filter we built. Maybe I can plumb it to suck up from the UG filter.

You certainly can.

I don't like under gravel filters. The aerobic (oxygen loving) bacteria does degrade the uneaten organic material (food and poopies) but you still end up with a rotting mess underneath the filter plates that is a large producer of ammonia -- which then get converted to nitrites and nitrates. People seem to think that the rotted food and fish poops seem to miraculously dissapear in the gravel, but it's all there in some form. And, should you happen to have a power failure, even for a couple of hours, then the aerobic bacteria in the gravel dies and when the electric comes back on, you wil have a brown, sludge of a mess coming up through the exhaust tubes. My opinion, stay with a cannister or external filter and do routine gravel vacuuming and water changes to remove crud from the gravel and nitrates from the water.