Undergravel filters

[jpappy789]

As a related question to this thread, is the mechanical filtration for this type of system the gravel vac'ing itself? Are there options with an undergravel filter system for removing fine particles or is it the gravel itself that traps debris that is removed by the vac? I must say I've been put off by the idea of an UGF system for the ease of the HOB with a biowheel. Perhaps I should rethink the UGF for a non-planted tank.

Essentially, yes. I believe there are ways to use a caniter or HOB as the driving force of the system (as opposed to an airstone or powerhead) but I've never tried it myself and not entirely sure how effective it is. With the reverse systems you generally use a prefilter to make sure no large particulates get lodged underneath the gravel. A secondary form of filtration is always a good option IMO, and it would be cheap and easy to find a HOB or something that is smaller than recommended, if used alone, to do the mechanical filtering.

 

[ecoomer45]

If you're just going with plastic plants, no problem. The ideal solution with a UGF is to also use a HOB filter for circulation. If you use powerheads, even better. With over 55 gallon tanks, powerheads are almost REQUIRED to keep good circulation under and thru the plates. UGF's are a bad idea for planted tanks, as the roots get wrapped up on and thru the plates and make knots. I know from experience that doing a rescape after the plants have been growing thru the plates for a while is a SERIOUS pain.

 

[jpappy789]

IME it depends on the plants. Mine never had deep enough roots so it wasn't a problem, even the crypts. I would imagine that a huge sword that has been established in the tank would be a major pain.

 

[sorberj]

I've had trouble with swords getting under the plates with the roots. The biggest issue I've had with my 55's ug system is that I somehow had some substrate that was finer than the grates. It worked its way under the plates and then traveled over and plugged up a lift tube. It was a pain to clean out, but the tank settled back down after a day or so. I do gravel vac with my weekly water changes and that seems to get everything cleaned up. I'm pretty heavily stocked and my Nitrates, Nitrites, and Ammonia have been 0 since the tank finished cycling.
I also recommend using a power head for any setup over 30 gal, but anything less than that and an air-pump driven system will get enough flow through the tank depending on how many lift-tubes you run. There's probably a calculation for the amount of airflow needed through the lift-tube based on the distance between tubes, but that seems oddly technical for one of the most old-school of filtration techniques.
The biggest issue I've seen with loss of effectiveness is when one tube gets overbalanced (i.e. a lot more flow than the others.). If that's the case, the heavy flow tube can start sucking water through the other tubes and bypass the gravel. Usually this happens when someone puts a 100gph power head on one tube and runs bubbles on another tube 10 inches away. Additionally, if you are using a bubble-driven UGF, you're ruling out the use of CO2 injection for plants since the bubbles will just carry it up and away, although there's an argument to be made that if you're investing in CO2, you probably are willing to shell out some cash for an expensive filter and thus make that point moot.
My biggest critique of UGF though is that there is a significant footprint in the tank that can get in the way of aquascaping. Those darn lift-tubes take up valuable space that could be used to build rock caves for my Krib and he just hasn't forgiven me for that. I'm hoping to upgrade soon and I'm going to go with a canister filter for that system, but I'm also going to start getting more serious about plants.