It all depends on the plants you are growing. Age, variety, size, breed. If you check over my hydro start 2015 thread i give all my ppm readings at start through current. Its a long read but clkingtx had alot of very good questions i answered which would give you an idea of where you want to start at through flowering. You can measure ppm right after mixing the nutrients, no need to wait. Ph you want to give it time to stabilize so i usually wait half an hour.

The reason they give different ratios of grow/micro/bloom is dependant alot on what you are growing. Lettuces like a 15ml grow/10ml micro/5ml bloom. Tomatoes like a 10/10/10. Peppers 5/10/15. Cucumbers 10/10/15. Etc.... Thats just a general ratio and not a strength concentration. 250-500ppm for starts are generally acceptable.

Using the floranova series i use 1/2tsp per gallon start, a few weeks later bump to 1tsp per gal, Then if the plants want it ill go higher. Youll know eventually just by looking at the plants what they want.

I'll revisit that thread. It will make more sense now. You guys are a great resource.

I think I made a mistake trying to grow lettuce and tomatoes in the same tank, now that I've seen the numbers. If I have to sacrifice one, it will be the tomatoes.

Id suggest just doing a few buckets beside the lettuce tub for tomatoes. A T off of the air pump and an air stone per bucket and voila a separate system to grow together. Check with your local deli's/donut/bake shop for free 5 gal buckets.

I may do one bucket. My pump has two outlets. I've got 2 disc-shaped airstones in my reservoir. Can I get by with one?

Yep. Im running 10 Buckets/ stones off of a cheap dual outlet walmart pump. Lettuce will grow without airstones so no biggie not having the air bubbling extremely well. If anything id focus on air to the maters than the lettuce.