Yup that is like mine also, that doesn't mean that you waited too long, it's what you should expect and what you want actually. That means your growth got into the 3D stage, so it traps water in that mass of algae but it's still flowing through it quite fast. You can see that if you slide one of the light fixtures sideways before you cut the flow - it drains out quickly.
The side effect of course is that when you pull out the screen, the growth that is stuck to the side tears away. But again, not unexpected. The growth is generally easily removed from the polycarbonate growth chamber with a single pass of the scraper, I usually have some that is more anchored to it also though, but I just leave that in place, there's really no reason to get the growth chamber super clean anyways, it's just going to grow right back.
Also the attachment to the growth chamber, in a way, helps to keep the growth in the chamber. You get support from the screen and from the growth chamber. I've noticed this actually has the effect of making the screen easier to harvest, the growth isn't as firmly attached.
It's kind of interesting, what I've noticed is that when you have an open-air screen or a screen in an enclosed box that does not fill it up with the 3D type growth (I still run a Rev 1 on one tank, it doesn't get as much 3D growth) that those screens have firmer attachment. It's like the algae sort of adapts. Like with the UAS units I've ran, since there is no gravity/waterfall force, the algae almost doesn't need to stay as firmly attached in order to stay in place, so it just doesn't form that tough attachment - it's easy to remove the growth. But with a large open air screen that is mature, that growth is very firmly attached and you sometimes need to really scrape hard to get it off. That doesn't seem to be the case with my Rev 4 L2, at least not so far (and it's been running long enough where I would have seen that)
