keep on with 1/4 strenght, at some point if ever the plants will look a little pale, thats when you up the nutes, let the plant dicatate to you how much to feed, also i dont know what the inside of your rez looks like but you can install a pump attatched to a pvc with a ball valve, so when you need to change it out just turn on the pump and open valve. im gonna go into my RIU and post a link to a grow who has his tubs setup like this

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SOL: It's the Russian. AVI:A Russian? SOL:To be technical hes Uzbekistanian?AVI:I been dealing with those Russian dogs. AVI:give me a name.SOL:Urinov,Boris TONY:BORIS the BLADE? as in BORIS THE BULLET DODGER?AVI:why do they call him the bullet dodger?TONY: bcus he dodges Bullets Avi