My frustration with the many articles I have seen on aquaponics/aquaculture is that the really good ones tend to be way over my head.
I found a good, basic article about water chemistry that I wanted to share with others: http://fins.actwin.com/mirror/begin-chem.html
I confess I'm apprehensive about the idea of using muratic acid to lower PH, but considering the serious PH issues/hardness of our tap water, plus the amount of evaporation that happens during the summer months, I recognize it will have to be done.
I don't see much information that accounts for the desert environment, either. Looking to learn more.
How often do people do water testing?
When I was actively running a system I leaned on a local high school FFA aquaculture program for advice. I think Red Mountain High School in Mesa has a program now. The department of education can let you know which schools have programs close to you. I do not recall regular water testing. They tuaght me to let the water stand for a week before adding it to the tank. We had an 1100 gallon water tank we used to maintain the water in the tank. The tank was black and vented. the chlorine and "nasties" int he water either evaporated or settled nicely. Every time we tested we were "sitting pretty" according to the students and faculty.
Not the direct answer you were asking I know. That is how we handled ours for several years though.
Will you be offering another class in the future? I'd like to get some training on muratic acid. While I use it in my pool on a regular basis, it makes me very nervous to use it with my animals.
I found a quality test kit from my local pool store. Thanks.
What else do you need to do to tap water? (Currently I use a commercial pond conditioner which I'm not thrilled with.) Do you dechlorinate naturally in a holding bin? Is our tap water naturally high in phosphates? Does muratic acid reduce phosphates as well as lower Ph?
I will be offering a series of classes on aquaponics and a few related subjects soon ;-). RE: muratic acid, here is the results of my experience. The chemical formula is HCl. Thus when it disassociates it breaks down in to H+ and Cl-. Since pH is the measure of how much H+ there is in your system, just a little HCl liberates enough hydrogen to dramatically decrease your pH. Conversely, the amount of Cl liberated is so small as to not have a negative effect on your animals, even less than the Cl in tap water and it appears to quickly dissipate.
Two downsides that I have seen. 1. Rapidly changing any water condition can have a negative effect on your organisms. So far I have not seen this but I have not done replicated experiments where the bad effects would be seen more easily.
2. Since neither the H nor the Cl sticks around, the change in the pH is not permanent so you have to be continually vigilant. The process of nitrification where ammonia is converted to nitrite then nitrate tends to decrease the pH. Once that process stabilized, so did my pH. Also I understand, decaying peat also has the effect of lowering pH.
P.S. In green water systems algae removes CO2 from the water. CO2 when dissolved in water created carbonic acid. As in Coca Cola, the more CO2 the lower the pH. The removal of CO2 by algae or water plants, prevents the creation of carbonic acid thus pushing the pH up.