Can't over water with oxygen. I run a deep water culture hydro system. (Each plant's roots are completely submerged in a 5 gallon bucket, thru a 8' net pot lid). As long as the solution is oxygenated and water temp is controlled it should not cause harm. In my system, each single cell bucket is top fed instantly acting as an oxygen generator, however I still have an airstone in each bucket, even the controller bucket.
Re: House and Garden, I've been told that the warning about not oxygenating your solution/controller tank was a misprint along with several other errors that occured during the Dutch to English translation and should be fixed soon. There are several inconsistencies with the nutrient calculator and the feed chart from the U.S. Distributor, but am told to go with the US feed chart from Humboldt Co.
A wise man recently explained oxygenated water in the most simplest form: It was another rainy day in Oregon and he pointed outside the grow store and said, you see all those bushes, trees, weeds, etc..? Sure I said, Well they have been getting rained and dumped on non stop for the past 3 weeks, and do they look like they are unhealthy? No he said, and they are thriving under these conditions because as the rain falls it gathers oxygen, and thus helps but does not harm the plants.. Just like soil and hydro, and especially the deep water culture I'm using as long as it's oxygenated overwatering shouldn't be the issue. Maybe the Rockwool is, try using rapid rooters