One of the trickier parts of keeping your freshwater aquarium healthy is maintaining the water chemistry. I should know, since some of my early mistakes led to the sad death of fish I had picked out and nurtured very carefully. Let me teach you a little bit about pH and taking care of the water in your tank, so you don't make the same mistakes! The acidity of your water is measured on the "pH scale", which ranges from 0 (very acid) to 14 (very alkaline). Neutral pH is right in the middle, rated 7.0.

Freshwater fish mostly like water that's between 5.0 and 9.0, but you'll need to check with your books and your fish store folks to tell you more about what YOUR fish need.

How do you know what the pH of your aquarium is? The most common test uses the chemical called "bromothymol blue" (usually abbreviated "BromoBlue"). You just fill a small vial halfway with your tank's water, then add one or two drops of the BromoBlue. Depending on the pH, the water in the vial will turn a shade of yellow, green, or blue.

Compare the color to a chart, and you'll know exactly where you stand. You can also get pre-treated strips of paper that you dip into the tank, or even a sophisticated pH meter, but the BromoBlue test is quick, simple, and inexpensive. So why is it so important to keep a close eye on your tank's pH? It can drop lower when plant and animal wastes start to decay in the tank, and once the pH gets below a certain point, all the bacteria that break down the wastes start to die or go dormant, so the fish start to choke on their own ammonium. Don't let this happen to your babies! You can fix a low pH by changing out the water (so that the buildup of wastes is removed or diluted), or by adding ordinary bicarbonate (baking) soda.

On the other end of the scale, your pH might get too high if you have a lot of fish and plants, as their exhaled carbon dioxide gets into the water. To lower the pH, get a pH-lowering chemical from your local pet/fish store - it's usually included in the kit you use to measure the pH in the first place. Do look at the ingredients though - if the chemical includes phosphates, it might encourage algae growth in your tank. Also, it's harder to alter the pH in hard water; if your tank seems to be resisting your changes, you might need to look at methods for softening the water first.

Love your fishies and study your tank everyday, getting used to how they normally look and act, and you can often spot the symptoms of a problem like pH imbalance all on your own!.

Together with Iszuddin Ismail, Mic Hudson is sharing his wealth of knowledge on fish tanks and aquariums. You can start with a free ebook on decorating your fish tanks. Download Fish Tank Aquascape at http://www.PetFishGuide.info