A TDS meter is not really of much use in Aquaponics since it actually measures conductivity of salts dissolved in water and won't really give you an accurate idea of nutrient levels in Aquaponics. About the only thing I've used a TDS meter in AP for is a not quite perfect method of kinda estimating the salt level in a system when needing to salt due to fish disease and for that I had to do dilution tests since the meter would only read up to about 1.8 ppt of salt.
I like using portable meters that can also be used for inline measurements. It's a great way to learn how your system works. There are some parameters that can't be measured using probes, so I use test kits. I purchased a meter from Forston Labs called the LabNavigator. It has the capability of measuring 4 parameters at the same time. Below is a screen shot of a fishless cycling study I've been working on.
Yea, and for a major commercial operation they would probably want something that could monitor real time and send out alerts if certain parameters are exceeded so that the on call manager could be paged and quick come in to deal with any problem overnight or whatever.
I'd love to be able to track things that way but I have to pick and choose my investments for the time being.
The freshwater master test kit and a thermometer should take care of most home scale aquaponics operations and even some small commercial ventures going with low density fish stocking.
I agree test kits are sufficient for hobbyists and commercial systems with low stocking densities. I like gadgets and with my background in wastewater treatment process control, I want to know what's going on and how the system responds to various changes.
What kind of fish should I use for my little tupperware tank study?
What kind of fish in your tupperware tank?
very small ones
If you have some other AP going on and could provide yourself with tiny tilapia fry or something that might work but more likely you need to get some type of fish that will stay small longer so you might be looking to the aquarium shop for some ideas.
I'm sure with a quick search on the internet and a trip to the aquarium shop you can pick up enough info about Guppies to get you through.