Freshwater angelfish are flat-bodied South American cichlids which hail from the slow-moving parts of the Amazon River and its tributaries. They have been bred in a number of color mutations for the aquarium trade ranging from the classic silver to gold or black or marbled. They work well in peaceful community tanks with other angelfish or similarly sized fish. Most angelfish used in the aquarium trade are captive-bred, and therefore do quite well in typical aquarium conditions.
Ideal pH for Angelfish
Though freshwater angelfish are hardy and will tolerate a wide range of water parameters, they prefer water which is softer and slightly acidic. The pH level can range from 6.5 to 7.1, though around 6.8 seems to be optimal for breeding.
Maintaining Proper pH
Maintaining a low pH can be difficult, as dechlorinated tap water often has a rather high pH.
To soften the water in your tank, or lower its buffering capacity so as to lower pH, try using distilled or reverse osmosis water for water changes.
Another way to soften your tank and maintain lower pH is to add peat to your power filter or substrate and decorate your tank with driftwood.
Keeping aerators and pumps low-flow will also decrease pH.
You can also buy additives which will help lower pH.
When you change pH levels in your tank, it is important to do it gradually. Consistency is more important than achieving an exact pH level.