What Time For Eheim Skimmer 350?

I would say on a smaller tank, like my 20g long it can have a large effect on CO2. I've played around with my skimmer more times than I should have. On full flow it can take my CO2 out of a good range quickly. I run it one click off of minimum flow, and I just run it all day, I found my CO2 fluctuates too much when I used to turn it off and on multiple times a day on a full flow setting, it was easier for me to get a constant CO2 with constant, lower skimmer flow. Right now I have mine come on when the CO2 starts, and stay on half an hour after the CO2 stops.

 

I get surface film on the water, and during the day this reduces the amount of O2 available to my critters. If the skimmer wasn't operating during the CO2 period, I would have to inject less CO2, or risk killing off my shrimp. The livestock are much happier with it operating during CO2 injection. I have it for the livestock, and I like the look of crystal clear water on the surface.

 

Your math adds up, but the table doesn't take into account anything that's in your water other than carbonate/bicarbonate, so it isn't particularly an accurate representation for YOUR tank water. Many of the things in your water affect the pH other than carbonates, and it would be one seriously complicated set of calculations to try to chart it out. Never mind the chart, it's just another way to convince yourself that your CO2 is better than it actually is!

You'll do plenty good enough if you periodically de-gas some of your water for a day or two, then measure the pH with a decent calibrated probe. Then, you just need to add enough CO2 (and diffuse it effectively, and circulate it effectively) to consistently drop the pH by 1.0 or so, when measured by that same probe.

 

I’ve only ever used an inline diffuser. The thing is, the deeper you have it in your plumbing the more time the little bubbles have a chance to come together into larger ones. After they get too big they just rise to the surface and pop as they exit the outflow tubing. The more gas you push into it the more gets wasted on ejection. I would say they aren’t very efficient by themselves. I now use the inline diffuser to feed a Sera 1000 reactor. I’ve never had a chance to use an in-tank version, I shied away from it because I didn’t want to clean it often. Feeding a reactor with an inline works better for me than feeding the reactor with regular bubbles. I feel like I have a limited amount of pump power in my setup, so the larger bubbles would fill the reactor fast and I would get a very large co2 buildup inside it. With the inline diffuser it breaks things down before the reactor, and I think it makes it easier for things to dissolve. I get a very fine misting of co2 in the tank, but not enough to detract from the tank, and the bigger bubbles get dissolved in the reactor. I’m definitely not an expert, because I’ve really only tinkered with this single tank setup. The combo is more effiecient for me. Others have used inline diffusers to feed regular reactors, like Edelry.junior. Then again you have Nuno M using an in tank diffuser and getting great results.

Over in Fablaus 20g journal there’s a couple videos of his co2 setup, and I posted a vid of what it looks like when you feed your sera with and inline diffuser.

20gl shallow tank - Plant Farm

TL;DR: Long story short there’s more than one way to skin a (CO2)cat. If I had to bet a nickel I would say the in tank version of the diffuser is more effiecient than the inline, because the bubbles have more space to expand, and dissolve. When they are in the aquarium tubing they come together into larger bubbles that don’t dissolve in the water as well.