Any tips for introducing CO2 to an established aquarium?

[Allan B.]

This is my first time adding CO2 to an aquarium. Were the CPDs reacting poorly to the CO2? If so, are there ways to safely introduce CO2 to an established aquarium without killing or stressing out its inhabitants?

I’ve got a 20 gallon long aquarium with amano shrimp, 12 celestial pearl danios, and one brittlenose pleco. I also have several Java fern, Java moss, and Anubis plants. Yesterday I introduced CO2 to the aquarium at 1 bubble per second, but after an hour 10 of the CPDs started schooling in the top right corner of the aquarium above a sponge filter. They were still very active and they didn’t seem to be gasping for air at the surface, but I stopped the CO2 and added a HOB filter to agitate the surface as a precaution. The CO2 drop checker was still blue, and my water parameters were all normal (zero ammonia and nitrites, 10 nitrates, 7.0 PH, 7 GH, 4 KH).

[Fish Folk]

On 11/12/2021 at 12:29 PM, Allan B. said:

This is my first time adding CO2 to an aquarium. Were the CPDs reacting poorly to the CO2? If so, are there ways to safely introduce CO2 to an established aquarium without killing or stressing out its inhabitants?

I’ve got a 20 gallon long aquarium with amano shrimp, 12 celestial pearl danios, and one brittlenose pleco. I also have several Java fern, Java moss, and Anubis plants. Yesterday I introduced CO2 to the aquarium at 1 bubble per second, but after an hour 10 of the CPDs started schooling in the top right corner of the aquarium above a sponge filter. They were still very active and they didn’t seem to be gasping for air at the surface, but I stopped the CO2 and added a HOB filter to agitate the surface as a precaution. The CO2 drop checker was still blue, and my water parameters were all normal (zero ammonia and nitrites, 10 nitrates, 7.0 PH, 7 GH, 4 KH).

I’ll qualify my 2-cents here by saying that I have minimal experience with CO2. What we found, however, was that _over time_ your buffer (hardness) will be lowered from CO2 infusion. If your water is already soft, what can happen once your buffer is worn down is a precipitous pH crash. Low, low, low pH can occur. Similarly, introduction of too much humic acid from leaf-litter breakdown can cut through and crash pH — but that’s different. Remember that plants _only_ use CO2 during daylight. At night, they require Oxygen. I’d recommend adding air to your tank to maximize the positive effects of adding small amount of CO2.

Edited November 12, 2021 by Fish Folk

[Mmiller2001]

I would increase surface agitation as much as possible. You want to maximize gaseous exchange for both CO2 and O2.

Here's my surface agitation and I also surface skim the tank.

https://youtu.be/7oCxiKw3ZyU

[DCT]

I recently went thru setting up pressurized CO2 in my 60 gal.  I was really nervous and afraid I'd mess up.  Yes I did.  Anyway if you carefully follow the instructions of when to turn on the CO2 and opening the valves you will have success.  Actually now that I think back I made two mistakes.  It was taking forever to get bubbles to come thru the diffuser.  I later learned that somehow I tightened the tube to the bubble station without including the rubber washer.  Duh.. the gas was escaping.  The second stupid thing I did was prior to discovering the first problem  Any way I remember making an adjustment (after the timer would have shut it off) and when I woke the next morning the CO2 was blasting though the tank and almost all my fish were at the top gasping for air.  I turned off the CO2 and did a major 75% water change.  I also removed all the fish I could while going thru this process.  Once the new water was added and it was safe I reintroduced the fish.  Luckily they were very resilient and nearly all survived my mistake.  My fish and plants are now happier than ever.  So hang in there.  Take your time and don't freak out.