For a long time you have been told potassium hydroxide and calcium hydroxide are the go to pH up minerals for pH up. While this does change the pH efficiently it doesn’t provide much benefit to the plants. This thinking was based on old hydroponic chemistry mostly based around chemistry models that had nothing to do with growing anything at all and more to do with just changing the pH. While it does accomplish the goal there are far more beneficial ways to adjust pH for aquaponics.
The much better way to adjust your pH is by alternating Potassium Silicate and Calcium Carbonate which both provide 2 benefits to your plants instead of one.
Potassium Silicate increases your silica levels which are almost universally deficient in aquaponic systems. Silica should be maintained above 60 ppms to ensure proper plant health and disease resistance in aquaponics. When above this threshold it dramatically increases disease resistance, increase crispness and longer storage time by as much as 7 days, reduce heat and cold stress including longer time to bolt on lettuce, and improved system health. It also adds additional potassium as well while raising pH similarly to other options. Potassium bicarbonate can also be used in a pinch to further boost alkalinity when needed.
Calcium Carbonate adds calcium and carbon to the water increasing your calcium and helping your microbes replicate far better than hydroxide. If you alkalinity (dissolved carbonate) gets to low is slows down microbial replication hamstringing your system.
This is why hydroxides while great for chemistry are a poor choice for aquaponics. By switching your pH up combo you can improve system health dramatically while reducing monthly costs on a range of related expenses.