[bodul67]

Good morning all. I have a 55gal deep substrate dirted tank with 3" sand capping with a 20gal sump filter. I have CO2 injection. I have a wave maker above diffuser to disperse co2 and on the other side of tank is another wave maker to circulate co2. This circulation does make a shimmering surface agitation. My question is should there be more agitation or no agitation for the o2/co2 balance. I've read so many websites & forums that for my size tank yes I should have more and some say no agitation. At the moment I can't get any pearling on plants. So confused.

 

[Quagulator]

You'll want a gentle ripple across the entirety of the surface.

You can always pump in more CO2 if you aren't getting enough.

Take a sample of tankwater with no CO2 in it (just before the CO2 comes on for the day for example) or leave a sample of tankwater out for 24 hours.

Measure pH.

Then measure pH of the tankwater directly from the tank after the CO2 is at it's peak for the day.

The drop in pH should be at least 1.0.

If it's not at a 1,0 drop, slowly increase the amount of CO2 you are using over a week or so - ensure you are around the tank whenever CO2 is being altered so you don't gas your fish. If your fish are gasping at the surface, dial the CO2 back slightly.

 

[minorhero]

How are you introducing co2 to the tank? What light are you using? What fertilizer are you using? These will help determine why your plants are not pearling.

As to agitation. There is a lot of disagreement on this because people are paranoid about co2 outgassing. If you are running something like an airstone or sponge filter, that can be a problem. For just about anything else its a non-issue. So you can run as much or as little surface agitation as you want and it will be fine either way. Your fish will get o2 from just the regular exchange with the tank and from healthy plants. So long as you don't gas your fish with too much co2 it will be fine.

 

[jellopuddinpop]

I highly recommend this article. It's very informative, and will completely answer the question you're asking.

Surface agitation in CO2 injected planted tanks - The 2Hr Aquarist

 

[Deanna]

I am a supporter of maximum gas exchange (I run CO2 24/7), which doesn't mean having the surface look like a boiling cauldron. I am dealing with a 29-gal and use a spray bar that moves water from the surface directly down to the substrate as one component, but a small, cheap, skimmer is a vital part of this and contributes up to about 50% of the gas exchange. You can gauge the level of your gas gas exchange with an O2 test kit, such as the Salifert kit. although the ppm measurement results may be questionable, the relative differences can be useful, much as a TDS meter is used. For example, with my skimmer turned off, the normal exchange of water layers from the spray bar results in a reading of ~8ppm O2 with the test kit. After a few hours with the skimmer turned on, the reading jumps to ~12ppm.

For calibration/reference purposes, you could temporarily drive heavy circulation with as many pumps as you can find and create almost unacceptable surface agitation (don't break the surface) and then, after a few hours of this, measure the O2, which will probably be near the maximum for your tank (supersaturation isn't good). Then, returning to your normal setup, you will be able to see how close you come to that high capability.