How to give your tank a really good deep clean.
Step away from the fish tank. The best way to do a deep clean, is to, not.
The best thing for fish is to do regular water changes every week, at least 50% for most tanks. If you don’t and then you do a larger than usual water change, then you could be in for a huge issue, potentially killing your fish.
Let me explain more.
In your water there are many things, one of which is calcium carbonate, or magnesium bicarbonate. This is your hardness, Calcium or magnesium as your GH, and the carbonates or bicarbonates are the KH.
As your filter process ammonia to nitrite and then on to nitrate hydrogen ions are released. They are acidic, in fact what makes anything acidic. But that KH, the carbonates and bicarbonates will mop them up, becoming carbonic acid, which will break apart and become water and CO2, the CO2 will escape as a gas.
This means that as more ammonia is produced, more hydrogen ions are released, more carbonates are used up, and the lower the pH becomes. Eventually all the KH is used up, and the pH will start to really drop.
Once it goes below pH6, or there abouts, most of the time your cycle will stall. But the ammonia being produced will be converted to ammonium by the hydrogen ions in the water. This is a lot safer than ammonia, it’s not safe, but it’s safer, think of it as being similar to nitrates. They’re not great as they build up, but they’re not immediately fatal.
Now you’ve got a time bomb waiting to go off. You do a water change, and in that fresh water are a load of KH molecules, they they go around and mop up some of those hydrogen molecules, and your pH will rise, and that safer ammonium, some will convert back to ammonia. Now your water is toxic to your fish, and it’s likely your filter microorganisms have died, or at least a lot of them will have.
Your fish start to die, you blame the water, something about tap water being awful, and the countries going to the dogs. You don’t do another water change till the algae gets so bad that you have to, and the process happens again.
What can you do. Test your water, with a liquid test kit, Ammonia, Nitrite, Nitrate, pH, KH and GH. Then test your tap water for Nitrates, pH, KH and GH.
Ideally they will match. If they do then you are good to go, change as much water as you like as often as you like. Ideally 50% or more weekly. This assumes that ammonia and nitrite are 0, and nitrates are less than 20ppm.
If the pH in your tank is below 6, then you will need to do small water changes, about 10% daily till the tap and tank waters match. Whilst you’re doing that test every day for ammonia, if you get any do an 80% water change, it’ll be a big pH change, but that’s safer than having ammonia. Keep testing and reduce how much you feed your fish.
If the pH is above 6, but there is a difference between tap and tank water, do 10% or so daily or twice daily till they match.
How to do a deep clean on your fish tank. Please don’t.
