I posted a link to an article about iron below. For your purposes, I think you would use both, because you would assume that your ph would be under control. There are different chelates, but they are all effective under a ph of about 6.5. Some aquaponics setups will run at a higher ph, around 7, but typical hydro is usually run closer to 6.

There's a lot more involved in iron absorption that just having the right ppm, as that article talks about. My idea with nutrients is to just have them available for the plant to use what it can when it needs it. That's a lot easier than worrying about precise ppm mixtures. I have used rusty barbed wire before to fix an iron deficiency.

Here is a link that might be useful: Iron Article

I had read that article and seen about iron messing with your pH. I mostly keep my ph around 6.2-6.5 (for tomatoes & peppers mostly), but this coming year I am going to branch out some on the different types of veg's I raise hydro style. I will be running 4 different systems and since it will easy to adjust the ppm to each system, I was going to try to do it. Using 35 gallon totes to hold the water solution (I have a small greenhouse and run one system outside in the summer for cukes). The main fertilizer (Southern Ag hydro) I use has some iron in it.

Neat. I had good luck with greenhouse cukes in a peat & compost mix last year. I'm going to try a few in hydro this year. "Sweet Success" is my favorite variety to grow.

The cuke I use is Jackson Classic (Johnny's Seeds). It is an idea pickling cuke. right size for a pint jar. Not to soft in the middle. Vines about 4-5 long, lots and lots of cukes. Draw back for general garden use is that when the hot July sun hits it, it dies. I grew mine in 35 gallons tokes last year and planning again for this year.

How do you keep the deer off your cukes? When I grew some, the deer had a hay day one night. And the plants were only about 10 feet from my house.

Dogs are the only deterrent I have found to be effective all the time. With everything else, like sprays, soap, rotten eggs, cayenne, garlic, sweaty shirts and 101 other smelly things, it really just depends upon how hungry your deer are and how much they like what you're growing.