Does aragonite need to be replaced with time?

[marciotf]

hi guys,
I have one simple doubt but cannot find a definitive answer so Id like to know from this forum that I trust: I currently have some aragonite in my freshwater tanks sumps to avoid too low ph. Does the aragonite capacity to increase ph diminish with time? Do I have to replace it at some point? If yes, how can I know whens the right time?

Thx very much.

 

[duanes]

I used aragonite in fluidized bed reactors, and periodically had to add extra after a while to maintain the fluid bed.
As acids build up between water changes from fish urine and other metabolism by-products, the calcium in aragonite dissolves. This will also depend on the buffering capacity of your make up water. My alkalinity out of the tap was @ 100ppm, and would maybe need to add a half cup every couple months.
The more you do water changes (if your water is neutral or above), the less it dissolves, the longer between changes (especially if tap is below 7pH), the faster it goes.