PPM Question

So I just got a TDS meter on Friday and I have a question, but here is my info first:

My tap water is around 300 ppm. I changed my res for the first time on 9/28 and added 55 ml of nutes. On Friday (10/5), my ppm was around 500 or so, so I added 30 ml more which brought it up to around 700 ppm. Yesterday (Sunday) it was down to a little under 500 ppm, so I added around 50 ml more nutes which brought the PPM to around 875. My reading tells me that 1000 PPM is about average, and 1500 and above gets into the danger zone by not allowing the roots to take in enough water. I am using organic nutes, but I keep forgetting to look at the brand. The plants are being fed for 15 minutes every 4 hours and they seem to be loving it, as the growth has gotten insane since adding more nutes and increasing feedings. They were planted on 9/17 and sprouted on 9/19.

My question is: Is it OK to add nutes often to keep the PPM up or what should I be doing with the PPMs. I haven't found very much info specifically on PPMs on the web.

Thanks for any help that can be provided!

Im brand new to growing hydro... so please don't take what I say into *complete* consideration... but I believe since the ppm should be around 400 or so for seedling lets say... then it would be MOST ideal for it to always be 400.. so if you could create a computer program or something to maintain 400 all the time.. it would be best.

I'm really interested in finding out the answer to this question too... :P

not sure bout ppm as most use ec readings if plants are hungry feed them
raise their in stages each week take it up a notch

only add nutes when ppm drops below half wat u set it at

e.g. if u set 600 ppm wait till it hits 300 then top up nutes


hope this helps

water

See, that was my original understanding of PPM levels too, but I also read that you shouldn't add nutes more than once a week, but I added nutes twice in 3 days and have so far only seen positive results. I haven't added anything full strength yet either, only 1/4 strength, so that also may play a role. Hopefully one of the gurus can help straight us noobs out.

what water said seems to make a lot of sense.
So if you are setting your ppm to 400, when it hits 200 in the reservoir, add more nutes to bring it back to 400 (or 500, or whatever)