Kalkwasser alone hasn't been keeping up with my calcium and alkalinity demands of my tank.  And I was walking though the electrical conduit section of Home Depot when I saw something that caught my eye and the result is this reactor.

Here's a picture showing the top of the reactor.  These are what caught my eye in Home Depot.  They are water tight conduit/chord plug fittings.  I didn't have a proper pump for my reactor, but I did have a Maji-jet 1200 (295 gph) powerhead.  So why not just enclose the powerhead inside the reactor?  That is what I did.  There is one line for the water/CO2 inlet (which runs into the suction of the powerhead), one line is the water outlet, one line is just to vent the top of the reactor and it is valved to either be dumped back into the sump or recycled back into the suction of the powerhead.  I open it to the sump when filling the reactor, but I keep it closed most of the time while it's running.  The other line is the power chord for the power head.

Here's a picture showing the power head.  The suction of the powerhead is drawn off the bottom of the reactor.  The 1/4" line going into the 1/2" suction is the influent water and CO2 and recycle water/CO2 from the top of the reactor.  The other line is the outlet of the reactor.  It is stuck down into the reactor to keep from drawing gaseous CO2 that might collect at the top of the reactor.

This is a picture of the bubble counter.  A normal bubble counter needs to be refilled with water occasionally.  This one is self filling.  The CO2 enters at the bottom and there is a short section of 1/8" rigid airline tubing stuck into the 1/4" CO2 inlet tube forming the bubble riser.  The line entering at the side is the incoming water.  This fills the bubble chamber and then the bubbles and water exit out the top of the reactor and into the suction of the power head.  The incoming water is supplied by my skimmer pump.

Here's a picture of it finished but empty.

Here it is full, ready for action.

It holds the better part of a 16 lb bag of Caribsea crushed coral.

What I quickly found out:  Those nifty little electrical fittings that I was so fond of aren't water tight.  They leaked like a sieve!  And I used a section of 3/8" tubing as a sheath for the power chord (with silicon inside the tubing).  This didn't work either, it leaked too.  So back to Home Depot and I came up with the fix pictured below.  They are just 1/2" threaded male to 1/2" slip adapters.  Then I tapped a 1/2" plug for a 1/4" John Guest fitting and glued the plug into the slip end of the adapter.  Viola, fixed!  I then took a 1/2" threaded plug and drilled a hole just big enough for the power chord to fit through (I had already cut the plug end).  I then pushed the power chord though the hole and filled the plug with 5 minute epoxy.  This plug threads in from the inside.

NO LEAKS!

Here it is set in place doing it's thing.

I have really been very surprised at how well my tank has taken to this reactor.  This has been an awesome project!

I bought the tube at NPS a few months back (I think I payed about $4 for a 6 foot length, and I used 18" of tube).  It's 4.5" OD, which is like $3 a foot at Regional Supply.

I had the powerhead laying around, but let's figure it's $25.  And I'll figure about $5 for the acrylic tube.  The other major cost is in the John Guest fittings and valves!  Those valves are like $5.50 each and it has 4 of them!  So the cost is somewhere around $70 (excluding media, CO2 tank and regulator).

So total cost for me was around $70 + $50 for CO2 bottle (thanks -tom) + $12 for CO2 + $22 for used regulator + $15 for crushed coral = $169

Very strange, but my pH has actually been better since adding this reactor!  It's swinging from 8.15 (day) to 7.9 (nite).

jon,

That's pretty nice!  Great work!

Mark Peterson wrote: If the time ever comes that I can get my mind back on aquariums again, I'll be asking how I can have one of these.

Whattt???? I know we havn't heard much from you but your mind not in the water?

And yes the project is awesome.  I'd love to be able to just think up thinks like that...and have them work.....and look nice....

I want to build me one of those

It all depends on turnover.  If your reactor effluent from the first stage is at about 11 meq/l and 6.5 pH, then not much is going to happen in any subsequent stage.  But if your first stage effluent is 8 meq/l and 6.5 pH, then a subsequent stage(s) would be beneficial.