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My qquarium has been having a number of issues lately, I had a pretty nasty infestation of blue green algea (cyanobacteria) which I'm controlling with more frequent water changes, and feeding less. I tried to get a few bottom feeding corys (we got a number of swordtail livebearers at the same time) but none of them did very well in my tank, in fact I think I only have 1 or 2 of the swordtails left.

I think they would have done better if I had more plants and hiding spaces in the tank, because these angel fish are starting to get a bit agressive, but my plants have stopped growing as rapidly as they once did. Also, some of my broader leaf plants are starting to turn a bit yellow and my water pH has gone way up, near 8. The angel fish love it, but that's a little too basic for my purposes as a community tank.

Since CO2 injections will lower pH, promote plant growth, and discourage algae growth, I think that's what I need to do to get the aquarium I see in my head. There are a few ways to add Co2 to your aquarium water:

• CO2 tablets: These are basically alka-seltzer for your aquarium.
• Yeast Fermentation: put sugar and water and yeast in a plastic bottle, put a pipe with the escaping CO2 gas into the water. It gets a little more complicated than that, but that's the basic principle.
• Electrolysis: This is not a very common method, at least in the US, but apparently is popular with German aquarists. Basically, a carbon rod has low voltage electricity ran through it, and as the Hydrogen and Oxygen split, some of the oxygen combines with the carbon in the carbon rod, and CO2 is released into the water.
• Compressed Gas: Tank of CO2. Regulator valve. bubbling pipe in the water.

Now, most of these option have some pros and cons:

CO2 Tablets:
• Pros: Cheap, easy.
• Cons: Doesn't really work.

Yeast Fermentation:
• Pros: Effective.
• Cons: Have to feed your yeast every few weeks, can accidentally pump yeasty-sugar water into your aquarium, and yeast bottles can explode if the line doesn't have a pressure release.

Electrolysis:
• Pros: Simple, put the inanimate carbon rod in water, plug it in, adjust the voltage.
• Cons: $120 to setup the system, $100 for new carbon rods, needed every 3-4 months.

Compressed Gas:
• Pros: Effective, cheap to refill, only need refilled every few years.
• Cons: Initial setup is a few hundred bucks, tanks can eventually go bad (but can be replaced when refilled.)

I'm thinking it's time to pick up the hardware needed to inject compressed gas into my tank.