Start at 50% nutes and go up to 100% using a PPM meter idealy. monitor during the increase....if no burning occurs then go up some more. I tend to stay at the recomendations on the bottle and maybe 10% more if they can take it...change solution weekly an flush monthly.
Re: Flushing...
^Not exactly Ms Fox....A true flush is draining the res completely and filling with Ph balanced water and idealy a Clearex type solution. At the least use straight water. This is too remove salts in your system so they wont get a lockout. Flush 24 hrs. Drain/refill/renute and do...
Re: Flushing...
2 weeks to flush will work but 4 weeks is normal. Dump your nutes aprox 7-10 days and flush monthly. The Ph dont matter as long as your in the spec 5.5-6.2