I recalibrated Ph meter it was reading 7.5 when it should have been reading 7.
I was growing with earth and I decided to try nft with rockwool as i've read of amazing yealds with it.
I did one previous grow with rockwool and was advised to keep watering system on 24/7 which I did without problems.
I've since spoken to others and one recomends 12hr on with lights and 12 hr off on the night cycle. the other recomends 15min on 45 min off, throughout the 24hr cycle which is what I have now.

Is it possible to rinse rockwool with H2o2 ( hydrogen peroxide) solution to kill any bacteria? If so how many ml per litre?