liquid CO2 sold in stores is a synthetic chemical (
glutaraldehyde C5H8O2) that is commonly used as a disinfectant. It is similar to chemical plants make. It has been claimed hat plants can use it as a source of carbon instead o CO2. I have seen no documented evidence that it does help plants. Also too much of it is toxic to fish and can kill them. Also some plants are damaged by it.
Fish exhaile CO2 and mixing air with water will cause some CO2 from the air to get into the water. So moving water is better than stagnate water. So some tanks may have enough CO2 in the water. But as of right now there is no way to measure CO2 in the water. There are some test kits that claim to measure it but they only work with pure water. Unfortunately aquarium water is never pure.
Other than light water and CO2 plants need minerals to grow. If just one single nutrient is missing you will not get any plant growth and the plant will eventually die and you will have algae issues. There are 14 nutrients other than CO2 that are needed for growth. If you cannot get floating plants to grow you have a fertilizer issue. Floating plants get all the CO2 they need from the air.
Some people have tap water with enough in it for good plant growth with a regular water change. other do very small or no water changes with the coal of using fish waist as a fertilizer. Most people have to use a fertilizer to grow plants. In my experience most plant problems are due to one or more nutrients in short supply rather than CO2. So you may want to try a fertilizer without liquid CO2 first before injecting CO2.
If you do decide to use CO2 there are2basic ways to do it:
- One methode is called passive CO2. This involves place an open inverted bottle in the tank with nor air in it. ig is then filled with CO2. The water then naturally pulls the CO2 out of the bottle as needed. When the inverted bottle is empty you refill it. Passive CO2 is self regulating and is very efficient and won't kill your fish with excessive CO2 levels. The CO2 can come sugar test reaction, acid carbonate reaction, or pressurize bottle. in my opinion this is the best methode to use.
- Others use CO2 diffusers but CO2 flow and pH need to be frequently checked to avoid getting to much CO2 into the aater. if that happens the fish die. Diffuser work best with pressurized CO2 gas cylinders