DIY Reverse flow undergravel filter - help!

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Imaginary.Fish

Feeder Fish
MFK Member
May 17, 2010
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Seattle, WA
I have a 110 gallon corner acrylic tank and I'm monkeying with the filtration system. It has an overflow with 1" pipe going down into the sump, and 1/2" return pipe into the tank. My idea is to make a reverse flow undergravel filter so that water is pumped in through the bottom, hopefully pushing the poo up to the overflow.

Right now I have a .22" thick piece of acrylic that is cut to fit the tank, and I plan to drill a bunch of holes in it, cover it with a fine mesh fiberglass screen, and put gravel on top. There would be PVC support under all of the edges, plus bits of it as "feet" here and there to support the piece of acrylic. The filter's return pipe would fit directly into the acrylic, flowing into the space under the gravel. I have two possible pumps I could use; one is 700 gph, the other is 950 gph.

Questions:

  1. How far off the bottom does the piece of acrylic need to be (that is, how much space do I need to give the water being pumped in at either 700 or 950 gallons per hour)?
  2. Would the amount of space needed be significantly greater if I used the bigger pump?
  3. What size holes should I drill in the acrylic, and how far apart should they be spaced?
  4. Is .22" acrylic (with supports) enough to hold a couple hundred pounds of gravel and rocks?
  5. Is this going to work, or am I completely nuts?
Any guidance you could provide would be very much appreciated!
 
JMHO A jet system would work better.

I think that the acrylic would possibly not stand up to the weight, I also think that the number os supports need will mes up the flow. I think you would need a lot of flow to get it to actually push anything through the rocks.

A jet system could have 3 or 6 jets that force the water up preventing anything from settling. if you need more you could put a power head on one side blowing to the other side. This would ensure that its hitting a jet and being forced up.
 
@ redman88 - thanks for the link! That is an interesting, and probably easier/better way to go about it. Still unsure how many pipes, what size, and how many holes to drill, though.

@ nfored - I thought about that, but it seems to me that you'd have to plan your entire tank layout (including rocks) in advance, which really limits your options if you ever want to redecorate. Also, my cichlids are very into digging and moving stuff around, so there's no guarantee that anything will stay where I put it. If I have a more uniform layout of water jets from below, I'm thinking that even if they totally redecorate the tank, there will still be enough water movement to keep it cleaner.
 
I built one and it didn't work very well, probably more to do with my design than anything. I removed it an plumbed my FX5 return to about 6" above the sand and it keeps it clear all the way across a 6' tank. It was much easier. On tanks without an fx5 I use small power heads in the corners to keep the sand clear.
 
I have one running in a 100 and am happy with it's performance.
http://www.monsterfishkeepers.com/forums/showthread.php?t=325689
More photo's in my album.
picture.php
 
@ Danger_Chicken - What was your design like? Any ideas on what went wrong? If there's anything you now know to avoid, please let me know!

@ dawnmarie - I checked out your albums, and you have some amazing setups! I particularly like the one with the noisy parts outside the house. Brilliant! Also nice to be able to see how you drilled holes in the pipes - looks like you drilled through the sides rather than just through the top. Good idea.
 
It's mostly true you are limited in layout with jets, but unless your fish are carrying huge rocks over the jet, it will just get blown out the way. I wish I had a video, my fish would swim to the top, then try to swim down through the jets. Good luck on the RUGF lets see some pics and status updates on how its working.
 
"Also, my cichlids are very into digging and moving stuff around,"
i've been thinking of setting up something like this but thats my worry is that they will dig a hole and the water will just flow out that.
 
I did all the holes with a cheap, used drill press.
All the holes are angled down and out at 45 degrees in two rows staggered at 1" OC.
The trick is to keep[ the "poo" in suspension and direct it to the suctions.
So far a 5X turnover is keeping it pretty clean.
I haven't needed to gravel vac in a month and the cartridges are doing 7 days without appreciable pressure increase.

My Cichlids have done a little digging, but, even if they were to expose a section of the grid it will only flow what the drilled hole(s) is/are capable of.

I'll stop short of saying it's foolproof, but so far it's pretty cool. (Thanks Ron)
 
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