Skimmers and PH. Help me think this through.

[Scorpius]

My skimmer's pump is rated around 290ish gph. The skimmer I'm looking at is around 650ish gph. Both of this skimmers take in almost the same exact amount of air, 900-1000 lph.

I run an airline outside which then goes through a co2 scrubber before being fed to my skimmer to combat low ph.

My question is this. Would the skimmer with the higher water rating, 650 gph, be better at driving out co2 from my tank water and help raise my ph even further? I think it would, but correct me if I'm wrong.

 

[Dan_P]

My skimmer's pump is rated around 290ish gph. The skimmer I'm looking at is around 650ish gph. Both of this skimmers take in almost the same exact amount of air, 900-1000 lph.

I run an airline outside which then goes through a co2 scrubber before being fed to my skimmer to combat low ph.

My question is this. Would the skimmer with the higher water rating, 650 gph, be better at driving out co2 from my tank water and help raise my ph even further? I think it would, but correct me if I'm wrong.

Designing a gas sparger is what you are asking about and there is not enough information here. The reactor dimensions are missing. Are the two skimmer bodies identical and do both hold the same volume of water while running?

 

[Scorpius]

Designing a gas sparger is what you are asking about and there is not enough information here. The reactor dimensions are missing. Are the two skimmer bodies identical and do both hold the same volume of water while running?

Nope. Ones a reef octopus and the other is a bubbke king.

 

[Dan_P]

Nope. Ones a reef octopus and the other is a bubbke king.

OK, there cannot be a direct comparison then. Here is one way to look at this problem.

Lower water velocity might strip more CO2 than higher water velocity, that is, stripping is more effective. The other part of the analysis is to determine the effectiveness of lowering the total amount of CO2 in the system. While higher water velocity is less effective at stripping CO2, it does process more water per hour and could turn out to be the better option than slower velocity In lowering the CO2 in the system. You can think of the slower velocity option as being more effective but wasting time. A similar mind twisting situation exists for dry vs wet skimming. Dry skimming (low foam flow) produces very concentrated skimmate. Wet skimming (high foam flow) produces dilute skimmate. You might guess that dry skimming is the way to go, but in practice, wet skimming more quickly reduces dissolved organic material in the system.

With the rate of CO2 stripping known for each device we might be able to see how effeciency translates into system wide effectiveness. We will need a chemical engineer to help us see our way through this morass.

 

[Randy Holmes-Farley Verified Community Expert]

It's too hard to judge the CO2 exchange effects of different devices without measuring it, IMO. If you already have both devices, I'd just try them and see which works best. The day to night pH swing size is a good indication of the aeration efficiency.

 

[Scorpius]

Thanks for the information guys. I appreciate it.

 

[NanJ]

It's too hard to judge the CO2 exchange effects of different devices without measuring it, IMO. If you already have both devices, I'd just try them and see which works best. The day to night pH swing size is a good indication of the aeration efficiency.

Can you explain why the day to night pH swing is an indicator of aeration efficiency? Is this assuming the skimmer runs 24 hours? Thanks

 

[Cory]

Can you explain why the day to night pH swing is an indicator of aeration efficiency? Is this assuming the skimmer runs 24 hours? Thanks

Because co2 lowers ph and is offgassed by a protein skimmer. If you offgas enough ph raises.

 

[Randy Holmes-Farley Verified Community Expert]

Can you explain why the day to night pH swing is an indicator of aeration efficiency? Is this assuming the skimmer runs 24 hours? Thanks

pH is determined mathematically by CO2 and alkalinity. If alk is even remotely stable, then pH swings are caused by changes in CO2, and for CO2 to change either means it is not equilibrated (incomplete aeration) with the home air, or the home air CO2 is changing on the same cycle.