The "stuff" won't grow as well if the water isn't flowing, so intermittent operation will help, as will a larger strainer. Here's the aftermarket digital control I installed on one of my AC's, and it works very well. Has the dehumidifier function you mention.
Another big help is to put a strip of copper foil, piece of copper tubing, etc. in there. It will act just like the copper anti-fouling bottom paint and reduce the growth in there. I've done this for years and it makes a significant difference. Stuff will still grow in there, but not nearly as fast. I also break up a Clorox toilet bowl tablet in half and put half in the strainer every time I clean it. This helps kill stuff in there and downstream.