DIY CO2 diffuser

This is very similar to the one I have made.

I use a 2 litre fizzy drink container. One additional thing I would use is some blue tac around the top of the bottle lid to help give an airtight seal.

The mix I use is 2 cups of brown sugar and 1 tsp of bakers yeast (you can also use brewers yeast)

I pour out 500 mls of boiling hot water, mix in the 2 cups of water until dissolved, then add cold water until it reaches 1000ml and then leave to cool to room temp. I then add the yeast and leave open over night. When you first get the CO2 there is a huge boost for the first 24hrs or so, and its best to leave it out of the tank as the rapid change in ph could stress your fish.

You can use a limewood diffuser or even a ceramic diffuser – personally I recommend the rhinox diffusers. I use them on both pressurised and DIY systems with good results.

The pH tests for aquariums are not very accurate. I would leave the tap water 24 hours in a glass jar before testing it. A lot of variables can alter how the test works immediately coming out of the tap.

I do not buffer against pH change and my water is very soft. I have read that buffering is only necessary when the kh is less than 3 degrees. This is one of the reasons that the EI (estimative index) is so good for plants. It negates may problems by doing weekly 50% water changes.

I dont personally run EI on my larger tanks, but closely monitored pH when I introduced CO2. I find a comparison of measured pH and using a drop checker proves an excellent combination of information.

Measured pH will tell you the tank parameters – i use a digital pH monitor I got off ebay, combined with a drop checker to give me a good idea of CO2 levels.

As regards your worries about Ph crashes.. if you use a fermentation CO2 it is almost impossible to overdose your aquarium – the safest way to preclude this is to wait the 24hours after making your solution before plugging it into the aquarium – as described above.

If you get into the chemistry of water pH it gets extremely confusing – especially if you get into the realms of discussing substrates which effect cation exchange capacity. I avoid a lot of that by introducing things slowly and monitoring closely.

Cool.. you’re a chemistry dude. I may have a few questions for you

The estimative index is a simple method which tries to avoid a lot of complexities and testing of tank water when growing plants.

Its main proponent in Tom Barr, who in a similar method to Diana Walstad, has used scientific methodology to explore the management of a planted aquarium.

An introduction to his method is here

But basically his theory is if you supply nutrients in excess to the plants they will grow unhindered and out compete algae for resources. This excess of nutrients is kept in check by large volume water changes.
hope this points you in the right direction …

@L777 wrote:

Well, actually my lab was mostly solid state stuff (predominantly x-ray and thermo techniques), so I really meant it when I said I knew *something* about aqueous chem. :oops:

Nice to see the dosing given in terms of mL and teaspoons — no access to the nice analytical scales anymore, and having a high precision scale “around the house” just doesn’t look good! :o

If I can keep picking your brain, what’s your favorite source of KNO3 and KH2PO4?

Great source for bulk fertz
http://www.bestaquariumregulator.com/ferts.html