These are refurbished earlier models that are as functional as my current hydroponic plant feeder apparatus. I explored several options like thickness of base plates, different size measurements, and using a one-piece base plate versus a two-piece base plate. There are other options i see possible, but my current model seems to work well for hydroponics and is easy to use and keep clean.
I think it is important to make the apparatus easy to work with regardless of what type of hydroponics tank one uses. The tank i use is made for indoor use with an eye for its decorative value. And of course it is fun to grow just about anything you can think of if you can.