[tmz]

Anyone else locally using one of these?

I just got an order of medical grade soda lime ( calcium hydroxide 76%, sodium hydroxide 4% ,water 19 % from Airgas.
$90 for 5 gallons which should take care of my 600 g system for over a year.
It is used by divers and medical patients who need the air they breathe purged of CO2.

For years there have been many questions about controlling excess CO2 with solutions ranging from open windows, open water with surface agitation , opposite photoperiod chaeto refugia, limewater dosing , piping in outside fresh air and so on. All of which can help. But it's always nice to have another tool,particularly one that seems so promising in terms of effectiveness.

I read about CO2 scrubbers on the Chemistry Forum. Some are now selling devices commercially and calling them CO2 arrestors. The idea is to pass air going to the skimmer air intake through a chamber where the CO2 from the incoming air is chemically removed.
One approach is to bubble it through limewater /kalkwasser). Unfortunately the limewater uses up it's oxide quickly,preciptates, and stops taking up CO2.
Another is to pass it through a chamber containing dry calcium hydroxide(kalk powder) but the powder will restrict skimmer airflow and simply letting the air pass over it limits it's effectiveness without frequently shaking it up.
The soda lime comes in granular form about the size of crushed coral pieces. It is designed for breathing apparatus and offers little to no air flow restriction. The commercial name for it is sofnolime. It has nice feature in that it changes from white to purple when it's exhausted.

I simply took a one gallon jug with a large cap and cut slits in the bottom with a dremmel wheel and glued on some feet( small pieces of egg crate) to allolw air to pass under the jug. Then I took a piece of hose that fit over my skimmer air intake hose; cut a hole to match it in the cap for the jug ; pushed the hose in and sealed it on the outside of the cap with some Plumber's goop. Done.

I added about a liter of soda lime to the jug and plugged in my skimmer air intake hose. Runs nice and quiet and there is no apparent air flow restriction.

I'll be tacking ph over the next couple of weeks to see how well it performs. Some who have used it have reported consistent bumps in ph by .2 to .4 units. eg from 8.0 to 8.2/.3 or even .4.

The idea is simple. This media absorbs the CO2 ,so the air bubbling in through the skimmer has none with an overall effect of reducing transient CO2 in the water which rasies the ph. The oxide in the calcium hydroxide and the sodium hydroxide link with the CO2 and form carbonate on the media which has enough moisture in it to facilitate the process.