sboisvert check out my post: http://www.cichlid-forum.com/phpBB/viewtopic.php?t=230368 I am thinking of doing something along the same lines.sboisvert said:I've read through the articles in the library on UGJ. Had a question though. It would seem to me that having 8 or so "large" jets would only cover a small portion of the aquarium (i.e. the gravel would only be "cleaned" around the jets and there would be dead spots where the gravel isn't "cleaned"
Has anyone thought about or done something more like an under gravel spray bar?
Guess another question, would be if hooking this up the output of an FX5 would be a good idea, possibly setting up a couple vertical spray bars in the corners to direct the flow/create a current back to the intake of the filter.
I would also agree that 8 or so jets in concentrated flow wouldn't cover all of the gravel and would result in dead spots. Pick up one or two of the water movers like the Hydro Koralia's or Tunze. These will flush most of the waste off the sand keeping the water moving over it. if you do go with two hook them up to a timer to alternate the flow pattern to also eliminate the powerheads from competing against each other.
I am not sure how much force you will get from the holes in the PVC if the spray bars above the gravel. If anything you will probably put more back pressure on canister resulting in GPH then you are currently getting into the tank. If you over sized the holes in the grid you would still have to problem with the first few holes pushing out all of the water and the remainder of the holes doing nothing. I was thinking... If you did decide to put the grid at the surface all over the place your Cichlids will also dig them up exposing all of the piping. UGLY!
If you put the PVC under the gravel and do some sort of Reverse UnderGravel Filter/Jet that may work but the only negative about hooking the PVC grid with holes up to your OUTLET of your canister filter is that most of the dissolved Oxygen in the water has been consumed by the bacteria in your canister resulting in less biological filtration within the gravel. If you don't care about extra filtration it should still help keep SOME waste from settling into the gravel. You will still need to vacuum the gravel though. Also if you do go with drilling the holes in the PVC make sure you point them towards the glass on angles and OVERSIZE the holes. I built a trial one for my 55 and over time the canister had a harder time pushing water though the piping network due to the holes slowly becoming coated with beneficial slime.