To obtain the optimal ph level in an aquarium I do not recommend using water conditioners that are on the market because sudden ph changes can create problems to your fish and plants.
I will try to give you some small tips for raising and lowering the pH level.
How to lower ph level in aquarium?
• CO2, the best solution to lower the PH level is to inject CO2 in water because it will help also the growth of your plants. Check PH/KH table before you start injecting CO2 in the aquarium.
• Low surface agitation, limiting the surface agitation will help you to keep the CO2 in the tank and in this way to lower the PH level. If you increase the surface agitation you increase also the gas exchange which means CO2 release.
• Reverse osmosis, dilute the aquarium water with reverse osmosis water, this is not a solution for long term because ph value will rise again.
• Peat, using peat will soften the water but unfortunately it is not recommended for beginners. Peat is placed into the filter but the result is quite unpredictable and that is why it is not recommended to new aquarists.
How to raise ph level in aquarium?
Raising the ph level is much easier because in this case you have to add some substances into water not to eliminate them.
• Aeration, this is the cheapest method to raise the ph level. As you know aeration will decrease CO2 concentration which means that the PH level will raise.
• Water changes, in time the ph level tends to decrease and you can counteract this by water changes.
• Rocks and substrates, on the market you find many types of rocks or substrates that will raise the ph level.
• Water conditioners, almost all pet shops sell water conditioners to raise the ph level but I do not recommend using such products.