All I can do is tell you what I did and still do. My grow is coco with perlite using Advanced Nutrients Sensi Coco that uses the ph perfect tech so it balances and maintains ph for up to 7 days if mixed correctly. I’ve gone as long as ten days without problems. On 350ml mug grows I fertigate every 2 hours with lights on and every 4 hours lights off. It’s overkill for sure but like you said with coco you can get away with this but the top of the coco was algae covered by the end, no problem for the plants tho. On the 60ml grow it gets fed every hour because I can hardly get anything in the bottle. When growing in 3 gal pots I fertigate 3-4 times a day to increase growth and yield. I’ve not used amended coco so no clue there. To help prevent slime buildup I put air stones in the res on a timer set to run 15 minutes every hour. This was enough for me to prevent the solution from going bad. From earlier experience I knew that too much air bubble in the feed will cause fast ph drift. I always use either rainwater or RO water because it’s easier to stabilize the ph for me. Not sure if any of this helps but if you want any other info just ask brother. Your solo cup experiment looks to have some promise.

Im a soil grower so ill have to leave this for the coco guys to answer, but i will do a coco grow this winter for the knowledge

@monkeydo cool thanks man.  Going to try to get it setup today (sooner the better for my plants sake lol)