Adjusting pH
Cautionary note: If you are uncomfortable with the handling of acids, do not proceed. This information is provided as a means of adjusting pH in aquaria. However, there is still a very real danger when using some of the chemicals mentioned. Always work in a well ventillated area and use proper safety equipment. Acid resistent rubber gloves, apron, goggles, and an approved respirator are always advised when working with strong acids. I've gotten the warning out of the way, so now we can proceed. I've always had problems with getting pH to stabilize at any value other than what comes from the tap and reverse osmosis generally remains stable at neutral when heavily aerated. The amount of water changes I do just to trigger spawning also negates any chance of using peat, oak leaves, alder cones or any other tannic substance as they just aren't fast enough to keep up without using very large holding containers.
As a result, in an effort to raise large numbers of blackwater fishes which require low pH, I started mixing acids to speed things along. If you fit into the group that the cautionary note is intended for, you can still use the same technique, but simply use a weaker acid. I would recommend starting with distilled white vinegar, aka acetic acid. You won't get the same bang for the buck as a strong acid, but allows even a beginner to use these techniques. I'm not going to teach an introduction to chemistry here because there are definitions of pH plastered all over the internet already.
My method is actually very simple. I use muriatic acid that is commonly sold in pool and hardware shops for the purpose of cleaning concrete and concrete pools. Even at the dilluted values sold, approximately 36 percent, it is highly caustic and there is an obvious cloud of vapor when first opening the container. If a laboratory hood is not available, always make sure that you are in a well ventillated area away from any kids or pets when working with the acid. There is a very real risk here, and I cannot stress this enough.
To make my stock solution, I add 1/4 cup of acid to 5 gallons of tap water. I use tap because the alkalinity stabilizes to a much more stable buffer. Always add acid to water, and not the other way around. Splashing and volitile reactions are possible if water is added to acid, and can cause serious injuries.
After the acid has been added, allow the water to sit and stabilize for a couple hours. I alway leave it overnight to make sure that it has had a chance to mix well. After this, I add a heavy dose of a high quality dechlorinator to finish the mixture. The stock solution is then stored in glass or plastic five gallon carboys. Even at this point, it is still very acidic and is not intended to be used straight into an aquarium. This is simply a dilluted stock solution. A small amount is placed into a one gallon plastic container with a tap on the side to allow easy access for dosing tank water.
The pH from my tap always runs in excess of 8.0 and often a lot higher. However, by adding 400 milliliters of stock solution per 5 gallons of tap, I can lower the pH to a much more reasonable 6.5! If the use of a strong acid is not viable, I highly recommend using this method with the vinegar mentioned above. I've been able to spawn several blackwater species with this technique. They would have still been possible, but would have required a lot more space and time that I don't have.
