Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Fish are more concerned about the minerals in the water than the pH, though 8 does seem a bit too high for most soft water fish (including a Betta).
Do you have tests for GH and KH? Seachem equilibrium is adding the minerals that are measured as GH.
pH is a measure of the H+ and OH- in the water.
RO has both, as water molecules break up and reform. Usually there is a balance between H+ and OH- so the end result is a balance. I do not know what is creating the imbalance in your water. When you start with RO water it does not take much of an imbalance to make large changes in the pH test results.
A buffer acts by holding on to either the H+, leaving excess OH- in the water, or holding on to the OH-, which leaves excess H+ in the water.
When there is more OH- a pH test will read over 7.0.
When there is more H+, a pH test will read under 7.0.
You can directly alter the pH of the water by adding H+ such as an acid. Makes the water acidic, low pH. Adding peat moss to the water before you add it to the tank can make the water more acidic. This is what I do for black water fish. You can add peat moss to the filter, but there is not a lot of room in your filter.
You can alter the pH of the water by adding OH-, which makes the water high pH. (The local water company does this, I called and asked)
Or you can add buffers that will stabilize the pH at a certain level. A buffer picks up and releases H+ or OH-, depending on what buffer you have, so that the levels in the water do not change so much.
This creates more stable parameters for the fish.
Bicarbonate buffers are the most common in the aquarium. This type of material picks up some of the H+, leaving the OH-, so the water becomes more alkaline.
I would do as Hoppy suggests: Add just enough potassium bicarbonate or sodium bicarbonate (baking soda) so your water in storage will test 1-3 German degrees of hardness. This should allow the pH to remain stable. I would also add a handful of peat moss to the 5 gallon bucket. It might take a little experimenting to find the right amount, or how long to leave it in. I use a knee-hi stocking full of peat moss for 24 hours when I am prepping 20-40 gallons of water. I reuse the peat moss several times, but treatment time gets longer after several uses. This will make the water more acidic.