CO2 Reactor

Recent activity in the PSG fish tank has centred more around the plants than the fish. We have been battling green algae for some months and have only managed to reduce it by adding some Flying Foxes. We use Bioplast fertiliser, although I am not convinced that it does any good at all. It also lists phosphate as one of its main ingredients, although the algae did not reduce when I stopped using it, so it may not be the cause of our current algae problem. I would like to try dosing with PMDD at some point, but would like to find a source of ready made powders, along with a clear set of guidelines as to how to judge their use.

CO2 injection is provided by a DIY yeast reactor, the recipe for which is one cup of sugar dissolved in hot water, diluted to about 1.75 litres with cold water and one teaspoon of baker's yeast. This mixture produces a good flow of CO2 for two to three weeks, after which the bulk of the water is drained off and replaced with more sugar water. Once every few months, the whole mixture is replaced.

The water output from the filter is directed along a piece of tubing and though a vertical wide pipe (actually a gravel cleaner that I no longer use). The CO2 enters at the bottom of the pipe, creating a large bubble of CO2 through which the water falls. This causes a lot more CO2 to be dissolved into the water than would have been possible otherwise. The picture (below) shows the reactor (which has now been moved behind the Amazon Swords shown at the left of the picture). You can see the pipe coming from the filter (far right back, behind the reactor) into the top of the reactor. The water moves downwards through the reactor and leaves at the bottom. The CO2 comes near the bottom of the reactor through the small clear tubing that you can see snaking away to the top of the tank. At the time of photographing, there was not much CO2 in the reactor. The gas normally fills the chamber, leaving the water level right at the bottom of the reactor.

This CO2 arrangement proved to be too successful and pushed the pH down too far !! We eventually removed the reactor shown above and just had the CO2 collect in an upturned plastic box in the tank. This seemed to keep the plants happy without turning the water into an acid bath !!