increasing CO2 levels while maintaining high pH

[Rick Lindsey]

Hi all, I'm trying to maintain a planted tanganyikan tank with little success. Even before every surface of my tank was covered with nasty brown algae, my plants were dying off. I only have ~1W/g of lighting, but this is eventually subject to change. For the meanwhile I'm going to try to stick to low-light plants. I have several Jungle Val in there now, and a single anubias.

Anyhow, back to my question -- once CO2 becomes a limiting factor in my aquarium (i.e. when i get better lights), is there any way to increase the CO2 while still maintaining the high pH (~8) that keeps my tangs happy? Looking at some of the charts from thekrib.com, it looks like the only way to have a pH of 8 and a CO2 that even approaches a normal non-injected tank is to have sky-high kH. Am I just SOL if I want both plants and african cichlids?

If it matters, my fish currently consist of some multi's, a pair of leleupi, and a handful of danios. Eventually the danios will be displaced by cyprichromis, and I might add some julies, but that will be the extent of the fish.

 

[ddaquaria]

Here is what I did in my Malawiian African tank:
1. added coral to the substrate (actually did the entire substate with coral and a bottom layer of laterite.
2. Added CO2.

Plants grew well and the fish did not show signs of stress.

 

[nicola]

ddaquaria, what plants do you put in you Malawi tank?? Whatever I put in my tank gets eaten!
Nicola.

 

[ddaquaria]

I had great success with spiral vals and several anubias varieties as well as java fern. The one experiment that suprised me the most was growing crypt spiralis with my peacock and red empress. (Important: I kept more meat eaters than plant eaters). After the crypt got 'use' to the tank, it took off like the vals.

 

[jowens]

Rick - there is a fixed relationship between hardness, pH, and CO2 levels. I really like this article's explanation of how it works:

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

Basically, if you increase your water's hardness at the same time as you increase CO2 levels, it's possible to maintain a constant pH level. The danger here lies in your CO2 supply. If your CO2 supply is inconsistent (i.e. runs out, or stops and starts), your pH level will be inconsistent too. If you CO2 level is constant, however, your pH will always be constant. The pH will be lower than it ordinarily would be for your hardness level - but it will not change. In a situation where you have a constant CO2 supply, all you have to do to raise the pH is add a little baking soda (kH). The baking soda increases the hardness, which in turn effects pH.

The myth of CO2 injection is that you'll experience unpredictable pH "crashes." The relationship between pH, CO2, and hardness is actually a mathematical equasion...and if you keep the ingredients constant, you can predict pH to a very precise level. But the key is consistency. Setting your hardness is easy. Controlling the amount of CO2 entering your tank with a DIY generator isn't always easy.

If you're using a DIY CO2 generator, the best way to ensure consistency is to replace your bottle of solution a few days before it's going to run out. This way, you're never in a situation where pH flies up when the CO2 supply goes dry. You always want a constant, strong supply of CO2 - and this is achieved by always keeping a fresh bottle of solution on hand. (Keep in mind that you need to mix the solution a day or two before using it in the tank. It takes a little time for the yeast and sugar to start to react.)

Or you can guy a 5-gallon CO2 tank and a regulator (overall, setting something like this up will run you around $150), which will give you pinpoint accuracy. This is what I use.

Keep in mind that it may be possible to grow as many plants as you want without using CO2. I would recommend upgrading your lighting and seeing how plants do with that alone. If they still struggle, then think about CO2 injection. If you have more than one planted tank you want to use CO2 on, I would recommend ponying up for the tank and regulator. A single CO2 tank will take care of as many aquariums as you want and you'll never have to worry about pH spikes.