DIY C02

Hi,

I added more light to my tank a couple of months ago to improve plant growth. I currently have around 2 watts per gallon. I decided not to go for CO2 and see if I’d manage without it. However, recently I experienced an algae bloom and started to look around for a C02 system. The cheaper systems are yeast based, but are only suitable for tanks up to 100l. Mines 230l so it wasn’t a runner unless I bought two of them.

Pressurised systems are more expensive working out at around €160 complete with a solenoid (on eBay). Before I splashed out, I decided to give the DIY CO2 method a go. I frequent a UK forum from time to time and many of the experienced members there highly recommend it.

The system is also very cheap to set up and maintain. Here’s what I needed:

2l lemonade bottle
0.5 litre lemonade bottle
Length of aquarium silicone tubing
Air stone
Non return valve
Sachet of bread making yeast (found in any supermarket)
Teaspoon of Baking Soda
Two cups of sugar

The first task was to drill holes in the bottle tops of a diameter slightly less than the diameter of the silicone tubing. One hole in the lid of the 2l bottle and two holes in the lid of the 0.5l bottle. I then fitted the silicone tubing into the holes – one from the 2l bottle into the 0.5l bottle and one from the 0.5l bottle into the tank. Then attach the air stone to the tank end. The 0.5 litre bottle allows you to count bubbles and also acts as a guard if the mixture in the 2l bottle bubbles over, i.e. not contaminating the tank.

The silicone tube is an airtight fit in the holes so has to be compressed when pushing it through. However, once there, it fits well and is air tight.

The next step is to create the mixture. Firstly fill the 2l bottle half way with warm water (not hot). Add the two cups of sugar and then swirl the mixture around. Then top up the bottle to three quarters full with cold water. Then add the sachet of yeast and swirl around to mix well into the mixture. You can also add a table spoon of baking soda which is supposed to stabilise the amout of CO2 released.

Then simply attach the cap to the 2l bottle (the one with one hole) and then fill the 0.5l bottle half way with water only. The silicone hoses into the 0.5l bottle should be about 4 inches long inside the bottle from the 2l bottle so it’s submerged in the water and about 1inch long inside the bottle going to the tank (not submerged in the water). The silicone hose inside the 2l bottle should be about an inch long inside the bottle (not submerged in the mixture).

Once connected up, you should start to see CO2 bubbles within 30 minutes or so.

The amount of C02 in the system can be monitored by checking your pH and KH. There is a table available online which allows you calculate the amount of C02 in your tank using these two readings.

www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

pH needs to be checked daily to ensure it remains stable. The higher your KH, the less issues you should have in this area.

My pH was 7.4 before I added the CO2 and dropped to 6.4 in 24 hours. This was a bit too much. Some recommend not to connect the bottle to the tank for 24 hours to avoid that initial burst of C02. The bottle should be left open in a ventilated area. Never cap a bottle with the mixture as it is likely to explode!

My pH has now stabilised at 6.8 and I have seen appreciable plant grown during the week. My plants are definitely looking healthier and are growing faster.

It’s also recommend to replace the mixture in the 2l bottle every two weeks to ensure an even flow of C02. I’ll have a second bottle and will prepare it the night before and leave it to vent. This will avoid the initial burst of C02 that I experience first time round.

This is worth a try if you feel you want to add CO2 but want to avoid the high cost. For me, it also had the added benefit of lowering my pH as it was a bit on the high side.

I can post some photos if anyone's interested.

Great post!

But I would make one suggestion to you. Using an airstone is not an efficient way of getting co2 into the water. This is because the bubble is released from the air-stone and it immediately rises to the surface and is expelled from the tank. What you wast to try and do is increase the amount of time that the co2 is in contact with the water thus increasing the amount of co2 diffusion into the water therefore helping to maximise plant growth. I am currently using a DIY co2 contraption myself at the start I used an air stone but it showed no results, I then made myself a co2 bell from the top of a liquid washing powder bottle and the results were far superior.

This is the first one I made





I have since upgraded to a commerical bell that is green (less conspicuous
) and has a greater surface area.

I also think that adding an entire packet of bakers yeast is overkill and the mix will only last you a week before all the sugar is gone. I use 1/4 of a teaspoon of bakers yeast in a 750ml bottle, that has 11/2 to 2 inches (1 cup approx) of sugar in the bottom of it. This mixture will last for about three weeks and is the best ratio I have found so far.

Hope this is some help.

Regards

Denis

Thanks Denis. I'll give that a try. It also makes sense to add less yeast. I think I over did it which impacted my pH for the first couple of days. Ideally I would like to keep the pH at around 7.0. 6.4 was pushing the limits and meant I had too much C02 in the tank. However, the fish looked fine.

Where did you get the commercial bell?

I got the bell in America last year, it cost be three dollars but I haven't seen one in shops around here. Manufactures/shops don't seem to want to sell them on there own as they can make more money out of selling an entire kit rather than the parts and allowing for people to to a DIY catalyst system.

The other option is to get a "Vario Diffusion Reactor". My brother got one recently and it works even better than the bell. The surface of the co2 bubble spends even more time in contact with the water. He got it from www.aquatics-online.co.uk at a cost of £14.99. It is designed for aquariums up to 200l and it does look rather large so would not be idea for anything under 100l. To give an idea of its size; it would roughly be the same size as a packet of Jacobs polo biscuits and in a 200l could easily be hidden.



Vario Diffusion Reactor