# plenum (reduce nitrate)



## killerbee (Aug 18, 2004)

Does anyone know if i build this will it help out nitrates in freshwater or is this just for salt water?

















Tank Information:
Tank Height = 24 inches 
Tank Width = 12 inches 
Tank Length = 48 inches 
Tank Size = 59.84 Gallon

Plenum
Most of the systems at GARF (all of the Bullet Proof Reefs ) use plenums and have been very successful. Plenums create a dead water space area under the substrate. This dead water space, along with the substrate, help in the denitrification process which lower the nitrates.

Below is a cut list for a plenum that will fit the tank you entered on the previous page.

Qty Size Description 
1 46 " x 10" Egg crate top 
2 46" 1 " PVC pipe rails 
2 8" 1 " PVC pipe ends 
5 6" 1 " PVC pipe Supports 
1 21" 1" Riser tube 
1 46 " x 10" Nylon Screening (middle) 
1 49 " x 13" Nylon Screening (bottom)

All of the parts to make your own plenum can be found in most hardware stores like Lowes or Home Depot. The Egg Crate is usually found in the Lighting section. PVC pipe is in the pumbing section. Nylon screening is usually found around the screen doors.

Plenum Sand Bed 
80 lbs. - CaribSea "Seaflor special Grade Reef Sand" 
15 lbs. - Garf Grunge

To assemble the plenum follow these directions
The egg crate usually comes in 2' x 4' sheets and can be found in most hardware stores like Lowes and Home Depot. Cut the egg crate to size (A pair of heavy utility scissors works well.) 
Place the Egg Crate panel on a flat surface..
Attach the PVC pipe rails to the egg crate using nylon tie wraps (no metal).
Attach the PVC pipe ends to the egg crate.
Space the PVC pipe supports evenly on the egg crate and attach.
Turn the assembly over.
Cut a hole in the Egg Crate large enough for the 1" riser tube to fit into. This hole can be anywhere you want it.
Cover the assembly with the larger piece of nylon screening and tie-wrap in place. It should hang over the sides.
Cut a V-shaped grove in one end of the riser tube with a small saw. This will allow the riser to sit on the bottom of the tank while water moves freely.
Cut the screening where the riser tube goes and insert the riser tube with the grove in first.
Place the plenum assembly in the tank and center it.
Cover the plenum with approximately 1 to 2 inchs of CaribSea "Seaflor special Grade Reef Sand.
Lay the smaller piece of screening in the tank centered. This helps keep burrowing critters from disturbing the bottom layer of sand.
Cover the screen with the rest of the CaribSea "Seaflor special Grade Reef Sand.
After all the rock is in the system, sprinkle the GARF Grunge or live sand over the rock and bottom of the tank.
Install a Power head on the riser tube and run it until Amonia and Nitrite readings are undetectable, then remove the power head and riser tube.


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## killerbee (Aug 18, 2004)

Bump, does anyone know? Mods?


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## DonH (Jan 25, 2003)

Don't know much about plenums but have heard of them being used in freshwater planted tanks. I have 3 issues with using a plenum for freshwater.

1) I think the substrate that you are using is aragonite based. Correct me if I'm wrong... If that's the case, the pH will increase probably above 8.0 which is not desireable for many South American fish (even though it can be tolerated).

2) What's to keep the deep gravel bed from producing hydrogen sulfide instead of just denitrification?

3) Saltwater plenums use live sand as a top layer which not only contain nitrifying bacteria but also organisms that sift through the sand. How will that be accomplished in freshwater?


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## killerbee (Aug 18, 2004)

thanks for the reply DonH:
My susbstrate is tahiti black sand (don't know if that is aragonite based). I got from petsmart:










here is what they say:

This 100% natural aquarium substrate will create a unique look in your fresh or saltwater aquarium. Contains no plastic coatings; simply rinse before use. Black "Tahitian Moon" sand creates a dramatic look in any underwater environment

As far as #2 and #3, I don't know.

BTW: my Ph is always 7.5, i recently got cypress wood center piece, so i will test water and see if that lowered the ph as driftwood does. (from what i've been reading)


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