Hey there I know that when you add microbes or its the hydrogaurd sometimes you will get that foam its weird. I know what your talking about though it happen the other week. I didn't do anything about it and the plants all stayed healthy did the res change this week and let it stay just plain pH'd water no foam, so add my nutes and the Hydrogaurd and cpl hours later foam but all pants/root were healthy. your plants look good as well as your roots i do see what you mean by "bound" up but that looks like they just twisted in that motion from the water movement if you look in the pic the water is moving the same way as the roots. If you don't like the little foam try without the Hydrogaurd just to see if its that but if they stay healthy I would leave it be๐ Happy Growing!
