I think you should understand that when people talk about nutrient PPM's they are talking about the amount of nutrients... not there total PPM's.
(well most of the guys are as they don't bother to do the subtraction because they are running either RO water or their tap water is very pure).
So if you have shit water that is full of all kinds of unknown shit and is 200 or 250 right from the tap. Don't say "Yeah I mixed up and I'm running 750 ppm"
Its hard to tell you exactly what your PPM should be as it depends on A. the type of nutrient your using and B. the type and health of your plant.
In general however... and bet your bottom dollar some dip shit is going to come in and post... just to be a a "hey look at me,,, nuh uh" little douche bag something different... but anyways, here are some good guidelines for straight up DWC, ebb/flow a little higher, Under current, A lot less. This is also assuming your not running some shit-bird "torture tent" with 85 degree temps and 25% humidity and 50 degree water.
VEG CYCLE:
rooting cuttings, 2-3 nodes 150-250 ppm, ph 5.5-5.8
small plants, visible roots 4-5 nodes 300-500, ph 5.8-6.1
7-8 nodes... looking like a plant now.. 600 PPM, maybe 700 PH.. let it float around 5.7-6.3
Big plants, like 4 weeks of veg 700- 800 PPM, I have never seen the need to feed any plant in veg more than 800. I HAVE fed them more, but that is called wasting money, and torturing the plants.
FLOWER CYCLE
1st week of 12/12... veg nutes 800, topping off with flower nutes
2nd week, still transitioning to flower nutes, 900-1000.
3rd week, 900-1000 with full flower nutes.. hit with bloom booster. STILL 900-1000
4th week, same, start to bump up to 1100-1200
5th week, 1200-1400 full tend to stay in higher ph. 6.0-6.3
6th week, back down to 1000
7th week, this really depends on the plants.. typically down to 700-800
8th week, below 600
After 8th week, two days with plain tap.
Chop, trim, hang, scrub everything, sell bulk, go to strip club, buy wife something nice, repeat process.
You should realize that starting around week 6 is when I really crank the humidifier and get below 40% humidity. Co2 is around 1000 ppm at this point and I try to keep temps below 80. This combo (with the lower nutirent levels) has served me best in terms of the best aroma, trich count, and overall yield. If I keep pushing them at high levels through week 7-8 all those things suffer.
The experienced guys will say it over and over, less is more. Maybe one way to think about is.. who is in better shape... some guy that just sits at the table and food is forced down his throat or the guy that has to climb some stairs and jog a little to a enjoy a reasonably sized meal. Its a dramatic euphemism but the basic tenant holds true. PLANTS ADAPT TO THEIR ENVIRONMENT. Let the soil go dry... plants grow more roots. Thrash the plants with a fan.... they stems get thicker. Provide less nutrients... they become more efficient in regards to uptake. When you burn a plant, your DAMAGING the roots and leaf tissue. If you starve a plant... your not doing permanent damage (most of the time), and they will quickly recover with more nutrition.
Hope this helps.