Algae Scrubber Disaster

[Jaws]

Actually I always remove it to clean it but the contamination happens before I replace the screen. It's definitely happening when I take it offline and remove the screen. I modified a large aquafuge in order to build a waterfall scrubber so that water from my sump gets pumped up to the top of the aquafuge and falls down the screen and empties out the bottom back into my sump. But because it's under my tank in the cabinet, I had to make it tall enough so that the bottom of the scrubber is above the top of my sump so it empties back into the sump. As a result the top of scrubber is only an inch and a half from the ceiling of my stand. When I pull the screen out I have to bend it over the top of the scrubber and it tends to squeeze a bit against the acrylic of the aquafuge and ends up straining a bit of the water that's in the algae back into the sump. Just water though, no algae and barely any water at all. That's why I'm so surprised at how quickly it affects the breathing and overall health of my fish. Within 5 minutes they start swimming into rocks and each other and their coloration looks horrible. Definitely looks like ammonia spiking to me. I just can't understand why its happening and how it's happening so quickly. I do have a large bioload but my parameters have been WAY better since adding the algae scrubber and they should be more reliable than this. It's a mature scrubber too so it's nice thick green hair algae that's growing.