For those with root rot issues check out Hydroguard. I used it on my last dwc and it helped allot!
Hydroguard Bio Fungicide from Growco Indoor Garden Supply
Also about the airstone, I recommend a air diffuser hose.
like
Fifth Season Gardening
Mine was cheaper and only like 2ft. After using airstones, I loved the diffuser hose. It is super easy to clean and can be reused over and over.
My suggestion would be not to glue the airstone to the bottom of the reserve. If anything they make suction cups that will hold them in place. Just easier to clean the reserve and I strongly recommend that every few weeks as well.