One very important water parameter for keeping fish is the pH of the water. pH is a scale that measures from 0-14 that determines if the water is basic or acidic. Having a measurement of 7 means the water is neutral, anything above 7 then the water is basic. Then anything that is under 7 is considered acidic. Every kind of fish needs a different level of pH, but they normally prefer to have a neutral pH close from 6.8 - 7.2. That rule of thumb is for typical community fish, however other types prefer different pH. For example, Cichlids typically prefer having a higher pH of 7.8 - 8.2.
Before starting your tank, it is important to find out what the pH of your water source is. My house for example has water that has a pH of 8.2. When I first started to have fish I tried a lot of different things to lower my pH to a more neutral pH. I tried having driftwood, which is known to lower pH. I also tried some chemicals that lowered the pH. The issue with doing the chemicals is that it ended up putting a lethal amount of phosphate in my tank. Also, it means that I need to add these chemicals to water every week when I did a water change.
I ended up quitting trying to change my pH in my tank. I had some warning from aquarium stores for running a community tank with such a high pH. The key with keeping fish is keeping everything as consistent as possible in the tank. I decided that for my tank it was more important keeping my aquarium at the same high pH rather than trying to change it all the time.
In the beginning I found out that the most important aspect of keeping fish at a higher pH is a slow acclimation. Whenever I get new fish I make sure that the acclimation period is close to an hour. How I do this is I put the new fish in a bucket right below my tank. Then I use an airtube to slowly drip aquarium water into the bucket. I make sure that this process takes close to an hour so the change is very slow for them.
After close to an hour of this I turn off my tank lights and I use a fishnet to transfer them from the bucket into the fishtank. I have found that if the fish survive the first two days after living in the tank, then they are normally in the clear. I have been doing this method for at least two years and since then, I have lost maybe 2 fish within a few days of purchase.
I have fish that aren’t supposed to be in water with a pH higher than 7.5 that are thriving in a much higher pH. That is because after they get used to the new tank, I keep all the parameters constant.