Res changes necessary with Pure Blend Pro?

Hey all! Ive got a 20 gallon bubbler which holds 15 gal of nutes. Ive got 5 calio clones from a friend :friends: freshly rooted crisscross patterned across its 16''x40'' lid. They are currently in a mix of 4 ml per gal PBP grow + 1/4 tea per gal epsom salts and lovin it. Ph with this strength and my tapwater so far has maintained 5.8-6 which me likes! The nutes havent seen 71 F and they for the most part stay at 66-68F. Now changing out 15 gal in this setup takes a lil time(too cheap for a pump right now) and is a pita. Are complete res changes necessary when using PBP and no problems are visible? Wouldnt a 50 percent change be almost as efficient? When plants are this small ie week 1 rooting i cant see myself changing the res for atleast a month unless disaster strikes! providing i add back nutes when i change or maybe change in between cycles and that would handle it? Is hydrogen peroxide a no no with PBP? Its my understanding that the nutrients are readily available and therefore shouldnt depend on beneficials but would benefit better in a sterile environment? Mediumless DWC works great with PBP and people weekly res changes so no beneficials are thriving in there. Right? IMO it does nothing more detrimental than the overhyped sm90 pirranah and similiar products but they are okay because the companies added a few more goodies to there peroxide? Right or wrong let me know what u guys think. How often if ever do i need to change my res and is h202 counteractive with PBP HYDRO_ORGANIC SOLUBLE FERTS? Texas Kid maybe this ones for you Keep it green

You saved up to make this post? lol You have a few questions I will try to address; first off, changing the rez has nothing to do with what brand of nutrients you use, but more the remaining balance you maintain within the rez. If you follow the Lucas method you may save some nutrient changes and use less nutrients but I think its better to know what balance is there. If you add nutes to top off to a mix that has depleted the solution of lets say P and you add more of the rest in the balance you can get an overfert of the less used N and K or micros. So unless you are willing to gamble to save a few rez changes you risk problems.
That being said you don't need to change out every week, I just gave the nutrient rep visiting me a heart attack!! lol When plants are smaller they draw much less and can go 3 weeks without a change, just top up to maintain levels. As they grow larger you will adjust this to every two weeks give or take. Mixing H2O2 with nutes can cause lock outs of some nutes so its better to run it in between changes for a couple hours, then dump it. And re-fill with new fresh nutes pre-mixed. H2O2 kills many beneficials as well as oxygenate the roots and kill pathogens. I would use a siphon to empty the rez, it works well and will get almost all the liquid, with a slight tilt at the end. A simple aquarium tube will work.

Thanks Badmf! I guess the only thing im still unsure about is the h202 and beneficials. As stated im using mediumless water culture so theres no place for the beneficials to colonize other than the rez and directly on the roots.... which when you are using watersoluble hydrospecific ferts everythings there for immediate uptake so what good are the beneficials doing other than running the risk of mutating and causing failure? Wouldnt a sterile environment be optimal? TIA

To get sterile means no beneficials too. In many aquariums they keep some "old" water behind for that purpose, I don't think it would hurt, but using h2o2 will; if your rez temps are in line then no h2o2 is needed.