I have been looking on line for ways to clean old air stones with many saying to soak in vinger, bleach with varying methods. I have recently gathered all my old clogged air stones, 60 varying in sizes and types, and decided to see if I could refurbish them rather than throwing them out. The procedure I used is as follows:
1. Rinse air stones in freshwater ( I used rainwater) lightly scrub off excess of built up dirt
2. Allow to dry
3. Boil in freshwater for 10 minutes
4. Soak in solution of 1 part household bleach to 3 parts fresh water for 24 hours
5. Remove from solution and place in a container of fresh water for 1 hour
Note: others suggest to connect to airline and bubble through for 5-10 min ( I had too many to keep changing every 10 minutes)
6. Drain water and refill with fresh water soaking for another 1/2 - 1 hour and add water treatment as stated on the water ager bottle used, this removes the bleach element that was used previously in step 4
7. Air Dry air stones completely once dry store for future use.
Note: others state to dry blowing through air via air pump (I think this is a waste of your time)
My result was good, all the stones I replaced within my tanks are running as good if not better than new.
The above is probably not required as much as when we ran UGFs as most sponge filters create bubbles in their own chamber without the aid of airstones.
Hope this proves helpful to others.