I used to run E&F and never had any problems with salt build up, but I did run out of room for my roots. You should change your res once a week or possibly more, since it is only 6 gallons which is not a lot of volume to work with. The plants use different nutes at different rates so you need to keep it fresh for optimum growth. I found I could let my veg plants go without a res change for about 3 weeks with little to no negative effects, but in flower the effects became noticable on day 10 of the same 12 gallon res, and nutrients started getting locked out.

As for when to use your flower nutes, I used to mix half grow and half flower nutes for the first two weeks and then only flower nutes from week three to 7, then flush for 5-7 days. Good luck! :thumbsup:
dejayou30 Reviewed by dejayou30 on . 1st timer hydro with PPM vs. salts ???s I'm going hydro for the first time and I am confused about salt build up and PPM levels. I'm using a small pvc ebb and flow system with a 6 gal tub. My clones are still fairly small and look fine. My question is when do I start to get concerned about salt build up? I'm sitting at a PPM of 775 and keeping the PH between 5.75 and 6.25 (usually right at 6). Is the PPMs the only indication of salt build up I have to keep an eye on? If so, when do I start getting freaked out about it? I've Rating: 5