How much current does a CO2 diffusor need?

[Knetter]

Hi all, Finnally i've got CO2 in my tank. It is a Dupla starter set including a small diffusor. I have connected it with a small powerhead pump to pump the wate through the cascade. Now i was wondering if the current is too big. It could cause co2 loss causes by too much water movement...Or it will create more watersurface to react with the co2...?What is true??

[GulfCoastAquarian]

If the water flowed too fast, it wouldn't have time to react with the CO2 gas, but eventually enough water would pass to dissolve the gas. The general recommendation for CO2 reactors is around 600 lph (160gph).

[Knetter]

Thanx Sam, is 600 lph not very big? I have an Eheim filter that pumps as half as you advised me. Would 300 lph not enough? Or would the reactor gets too little fresh water to react with?

[GulfCoastAquarian]

600 liters per hour is not very big at all. The Eheim you're talking about is probably 300 gallons per hour, which is more like 1100 lph.
300 lph (80gph) should work, though.

[GulfCoastAquarian]

600 lph is not very big at all. What would worry me about putting the reactor in line with your Eheim is that it would slow the flow rate down from 300lph even further, reducing water movement, filtration efficiency and also CO2 diffusion. The Eheim 2211 is rated for up to a 150l tank so it's already a bit overtaxed.
Honestly, you might even be better off getting a second Eheim 2211 and putting the CO2 reactor in there. Together, they would improve water circulation in the tank and reduce the time spent cleaning out an overtaxed filter.

[Knetter]

OK! I always tought that a filter wasn't so much important for a heavily planted tank. Maybe i have to think to buy a new filter (although, my money is already spent on a CO2 set )....great thanks for the advise, Sam..

[Raul-7]

Here's what George Booth(America's own "Mr. Dupla") said-

"Since I'm always looking for ways to reduce the cost of setting up an aquarium, I was looking for a way to get CO2 into the tank without using a costly commercial reactor. Since about the only important thing is to give the CO2 enough time to diffuse into the water, I wondered if I could just bubble CO2 into the inlet of the Eheim canister filter and let it thrash around in the inlet hose, bounce around in the Ehfie-stuff, etc. And, by gum, it works!

To do it, I made a small hole in the inlet strainer and inserted one of those $0.59 right angle air-line connectors in the hole. I strapped the CO2 hose to the inlet pipe with a couple of small cable ties and connected it to the angle connector. To monitor the CO2 flow and to provide a check valve, I use a Dupla Bubble Counter, but that's not absolutely necessary - you can see the bubbles in the Ehiem hose if you watch real close.

I was concerned about bubbles collecting at the top of the Ehiem and "air locking" it, but it seems to be self clearing. About every 1/2 hour, I'll hear a gurgling and see some bubbles come out of the spray bar. I've found that the angle of the spray bar flow is important - if it's parallel to the surface, the increased surface agitation allows too much CO2 to escape to the atmosphere (I know, I know, I'm partly responsible for the Green House Effect :-). By slightly turning the spray bar towards the bottom, I still get some surface agitation and don't lose much CO2.

After setting it up, I was curious how much CO2 was being diffused into the water by my Dupla reactor and the Eheim filter "reactor".

With the Eheim, I measured the pH coming out of the spray bar using a LaMotte test kit and got 6.8 (23 mg/l dissolved CO2) with the general tank water at 7.0 (15 mg/l). This is surprisingly good for a "free" reactor."

[Knetter]

Wow, that sounds like great results! I had that setup too, when i was using the sugar/yeast method. The CO2 dissolved good in the water but what i disliked more were the bubbles of the Co2 "puffings". I've also heard that pure CO2 bubbles can damage your fish's skin.