Rex's Planted Tank Guide

Your Source Of Information For Planted Tank Aquariums, Lighting, CO2 & Fertilizers

How to Build a CO2 Reactor

This is the new and improved 7 piece DIY CO2 reactor. The old reactor has been retired. Make sure to completely read and understand these directions before attempting assembly of a reactor. PVC cement is not forgiving at all.

Rex's D.I.Y Reactor.

These pieces should be pretty easy to find for most people at a decent hardware store.
These pieces should be pretty easy to find for most people at a decent hardware store such as Home Depot or Lowe's.
A – 2” reducing T with 3/4” threaded side port.
B – 2” Coupling slip.
C – 2” Reducer bushing with 3/4” threaded port.
D – 2” Plug.
E - 15” 2” PVC pipe.
A on piece E
Piece A on piece E.
D inserted in piece A
Piece D inserted in piece A.
B on opposite end of piece E
Piece B on opposite end of piece E.
C in piece B
Piece C in piece B.
Picture of finished product
Picture of finished product.
Close-up of the tubing going into the reactor body
Close–up of the tubing going into the reactor body.

Now pay attention. You will need to use a proper cement to assemble this thing. You can use either the separate solvent and cement or one of the one part cements. Make sure that the stuff you use is for PVC use. It's best to assemble the unit from bottom to top.

And now the real test. If you read through these directions you might have noticed that there is no place for the CO2 to be injected. Assemble parts D, A, and E. Measure down 2” from the top of your pipe. Make a mark. Now take an 11/64 inch drill bit and drill a hole through the pipe on that mark. The 11/64 works perfectly with the Clippard tubing I use. If you use another type of tubing your mileage will vary. Now cut the tubing at an angle. Thread this angle through the hole. Take your needle nosed pliers and pull the tubing through the hole. Pull enough tubing through so that when you trim the end it will me in the middle of the pipe. Now finish assembling the reactor.

I use no media in the reactor. Just plain old physics will dissolve the CO2. With a 15” piece of PVC pipe you can use this reactor on most all canister filters. If you are moving a lot of water you might want to go a bit larger.

Make sure to use either Teflon tape or pipe joint compound (PVC safe) on the threads for the hose barbs. I almost always have these reactors available for those who don't want to mess with building one. I always have 5/8” elbows to fit these. Also 1/2” and 3/4” elbows. The 5/8” are much harder to find than the other two sizes. If you have questions feel free to ask.

How to Build a Regulator

Rex's D.I.Y. Regulator.

New regulator out of the box.
This is the regulator out of the box. We will be removing the large hose barb.
Removed hose barb
Hose barb removed.
Place adapter into the port
The adapter ready to place into the port where the hose barb was. This adapter is a 1/4” to 1/8” adapter. Note the use of pipe dope (the white stuff), I use a non-hardening pipe dope so I can later disassemble the regulator if needed.
Adapter installed.
Adapter installed.
1/8 hex nipple into the adapter
I have just installed a 1/8” hex nipple into the adapter.
Solenoid installed on to the hex nipple
Solenoid installed on to the hex nipple. Again using pipe dope on all connections. Ignore the thumb.
Low Pressure regulator
Clippard Low Pressure regulator installed into solenoid and needle valve installed into LPR.

That's pretty much it. If you are not using a solenoid and/pr a LPR then you just use another pipe nipple and coupling along with a 1/8” to 10-32 adapter to mount the needle valve. I can build a regulator for you if you wish. See the Sale Page. All parts show are also available.

Test Kits

For a planted tank there are a few test kits that you really should have on hand. These are pH, kH, gH, nitrate, and phosphate. Don't waste your money on iron test kits as they are very unreliable and not worth the money. Same goes for potassium test kits. So you might ask how does one know how much potassium to add. See the section on Fertilizers for that answer.

As far as what test kits work best. Well Lamotte are the best, but they run around $70 each. What I use is the Wardley's mid-range pH test kit, the Aquarium Pharmaceuticals gH and kH, and the Red Sea nitrate and phosphate test kits. One of my Bit's Of Wisdom is “Never test your test kit in your tank”. Now I'm going to tell you how to test your Nitrate test kit.

Testing Your Nitrate Test Kit

  • Take 1000ml of water. Dissolve 6.5 grams of KNO3 in it.
  • Take 1 gallon of water. Each ml of the above solution will add 1 ppm of NO3.
  • Add 5 ml, test. Your test kit should show 5 ppm.
  • Add 5 more ml, test. Your test kit should show 10 ppm
  • Repeat through the range of your test kit.