Bubble counter and water chemistry questions

[Linariel]

First question:
I've been reading articles for a few days now, but I can't seem to figure out exactly what a bubble counter does. Could someone please explain to me what purpose it serves? I mean, obviously it counts bubbles, but I don't know why you need to do that. Everything I've read assumes you already know.

Second question: I read on a couple of sites(Rex Grigg's included) that iron test kits are useless. So how do I know how much iron is in my water, to determine if I need to add fertilizer or not?

Third, and last:
What water chemistry test kits would you all recommend? I've never bought test kits before, so I have no clue where to start.

Thanks, and sorry if these are repeat questions. I ran several searches but I couldn't find these specific answers.

[Mgamer20o0]

bubble counters are that. so you can count the bubbles. just another way to make sure everything is working.

iron kind of hit and miss. you have to watch for signs of deficiency. add some and watch then see if you need more. this is what i do. if there is a better way i hope someone points it out to me.

i use api master kit. cheap and easy. i would just stay away from the test strips.