to top off res with just water or add nutes .

hi ive got a newb question. when i currently top off my resovoir every other day i just use plain RO water . am i to add nutes to this water instead ? i flood 5 times per 12/12 and am moving up to 6 floods slowly and the water lvl drops alot would extra nutes be benificial ?

if using ro water i would at least add some cal-mag to it.

The key thing you left out is how much water is being used every day? Just keep in mind that every time you add plain water you dilute the nutrient density. If you are adding a couple quarts to a 10 gal res no problem. But say it is down to 8 gal. If you add 2 gal of plain water you dilute by 20% and if you wanted your nutes at, say 1000, they may now be below 800. I add the needed water then check ppm then add nutes accordingly if out of range.

ok i havent been doing that, im glad i asked . thanks . i use a 45 gal res and ya im adding atleast 3 plus gal every other day

Just my 2 cents, but I've found that if the plants are using up the nutrient solution unusually quickly (during a warm spell or something) that backing off a tad on the nute levels (by say, slightly diluting the solution with plain water) can help prevent nute burn and salt buildup.

But then again I'd rather slightly under fert than over fert, so it mught just be me.