Which CO2 solution is best?
So you have decided to take the plunge and get a CO2 system for you aquarium. You’ve done a bit of research and probably come across 3 seemingly viable options – an aquarium CO2 regulator with large CO2 bottle, a small Nano CO2 kit with disposable bottles and a CO2 generator using citric acid and baking soda - but which one is best?
When researching CO2 for the first time, many people can be drawn to alternatives to traditional aquarium regulators because of the upfront costs. A disposable CO2 kit can cost as little as $70 and CO2 generators can be bought anywhere from $200-$300, compared to a reliably branded CO2 regulator setup which can cost anywhere from $300 upwards (for a full kit with bottle etc.). When comparing these prices, it almost seems like a no-brainer to go for the cheaper options – but two things that aren’t so obvious when comparing the upfront costs are running costs and reliability costs.
A disposable CO2 kit (i.e. Fluval) is the cheapest option upfront. A 45gram kit can be bought for as little as $90 and comes with everything you need to get started (diffuser, tubing, bubble counter, check valve). However there are several major limitations to these kits – firstly, they have no solenoid. This means that each day you need to manually set the CO2 levels, which after a few days can become and absolute pain. As the bottles are so small, the pressure can actually change very quickly and the levels you set in the morning will often not be the same in the afternoon. This is problematic as fluctuations in CO2 can lead to algae. Secondly, the cost of CO2 per gram in astronomical! A 3-pack refill of the 45g cartridges costs around $60. This works out to be almost $330 per kilo of CO2! Compared this to a regular 2.6kg bottle refill, which is usually around $30. When you factor in the cost of CO2 and the inconvenience of not having a solenoid, these kits quickly become unviable.
CO2 generators are a relatively new alternative to a traditional CO2 setup. They are more cost effective than disposable kits, however they have their limitations as well. Firstly, the costs of refilling these kits with citric acid and baking soda are comparable to refilling a regular CO2 bottle. Secondly, because these kits rely on generating CO2 within the canister, pressure will not always be consistent. Furthermore, although the canister is the same size as a regular CO2 bottle, it does not hold nearly as much CO2 making them unviable for tanks larger than around 60-100L without constant refills.
So that leaves us with traditional style CO2 regulators. Aquarium CO2 regulators range in price from anywhere between $80-$280. Although a cheap one will work, they have some limitations, mainly being that they can be unreliable. They are more difficult to adjust and it’s not uncommon for parts like the solenoid to stop working. Also, as they are single stage regulators they can also pose a risk to fish and other livestock when the tank is running out of CO2. Towards the end of the tank an influx of pressure can occur and a large amount of CO2 can be released into the tank, essentially gassing the inhabitants (known as end of tank dump). A dual stage CO2 regulator keeps the pressure coming out of the bottle at a constant level that cannot fluctuate.
CO2 can be intimating when first starting out, and alternatives to a traditional CO2 setup can be appealing to new hobbyists for a variety of reasons. When we factor long-term costs of CO2, reliability and convenience, a traditional aquarium CO2 regulator is always the best way to go. If budget allows, a quality dual-stage CO2 regulator will outperform and outlast a cheaper, single-stage CO2 regulator.
