Do macro algea use Co2?

[jt_redmist]

I know that people who keep freshwater plants use Co2 to boost the growth of their plants. Since macro algea such as cheato is also some kind of plant, is it safe to assume that macro algae also absorbs Co2? If so, wouldn't it be a good idea to drip the Ca reactor effluent into the refugium to have the macro algae absorb some of the Co2? I know most people use their refugium to absorb phosphates, but my concern right now is Co2. Just a thought. Correct me if I'm wrong.

JT

[boxfishpooalot]

Yes Macro algae do use Co2, probably one of their biggest things used durring photosythesis. The process by wich light energy is converted into sugar.

six molecules of water plus six molecules of carbon dioxide produce one molecule of sugar plus six molecules of oxygen. This is photosythesis.

But keep in mind that when photosythesis stops(at night) they release Co2 and take in O2(oxygen). So you may not gain much benefit at night.

[Boomer]

Chaeto's is usually not considered a macro but a "hair algae" where most use CO2. The larger blade true" macro's use mostly use HCO3- / bicarbonate, which there is lots of in seawater. CO2 in the avg reef tank is very small, on the order of 0.25 - 1.00 mg / l. Almost always, the higher the Alk the higher the CO2 and HCO3-. At a pH of 8.2-8.3 the CO2 dose not even reach a level of 1.00 mg / l, even if the Alk is 4 meq/ l. pH's in the very low 8's and high 7's can get you up to 2 mg / l.

[Randy Holmes-Farley]

Whether they use CO2 or HCO3-, macroalgae have the net effect of removing CO2 from the water, and raising the tank pH for that reason.

Whether they would grow faster or slower if put into the effluent from a CaCO3/CO2 reactor, I do not know, since I do not know their pH optimum for growth, nor whether they are ever CO2/HCO3- limited in normal reef aquaria.

[jt_redmist]

Thx guys for all the replies. I at least know where I stand, sort of :)

[Randy Holmes-Farley]

You're welcome.

Happy Reefing. :)