Hey buddy, just came across your thread. Dig the DIY nature as I am a huge DIY guy myself. Couple comments that may help (cause everyone has opinions
)
1. Dilute your PH down before you put it in the tank!! Like 10:1. It easier to adjust the ph (cause your just pouring it in cause it has less of an affect) and more importantly, your not causing nutrients to drop out of suspension by adding EXTREMELY acidic fluid to your rez. Those little grey clouds when you add straight ph adjuster.. those are expensive nutrients going bye bye.
2. You might want to change out your rez every week around weeks 3-6 of flower. The plants suck up ALLOT of nutes in diproportionate amounts and things can get locked out pretty quickly. On the other hand, I make my 50 gallon rez last a month during early veg.
3. Wash and SOAK your hydroton for at least a couple days to stabilize the PH.
4. Don't let your PH get above 6.5 before you knock it back down if you can help it.
5. painting plastic is a mother fucker and it takes ALLOT of paint to do it. Wrap them in some panda film and call it good.