Bad luck. The importance of filter capacity is easy to overlook.
Bacteria in the filter are deriving their energy from simple sugars, complex hydrocarbons, saccharides, lipids, org-acids etc. When you trim plants and when they decay these molecules enter the water and have to be fully consumed by the filter. It's a bit like when you cut a plant and bubbles come out for the next few days. Well a cocktail of different compounds including many plant growth hormones are released into the water and become available to algae. And here is the big difference.
Whereas we know that the nitrogen cycle is controlled by smaller filters - this is also a bit like saying transforming the species of nitrogen is enough to stop algae. Algae will use any form of nitrogen and this is why it occurs in tanks without ammonia. Check out what Tom Barr thinks on this subject. His view is that it is all about balance. Perhaps. But the most important thing to bacteria and algae will always be sugar (carbon) availability. They are in direct competition.
The reason people use bigger filter capacity is to remove the more complex hydrocarbon load. You still need to get rid of ammonia - but this is not the point of a bigger filter. You need to knock out plant growth hormones and all that carbon-rich food that algae love, and this will not happen without enough bacteria. In fact there are many highly desirable filter bacteria (other than nitrifying bacteria) that take quite a while to digest certain hydrocarbons.
The reason the industry pushes nitrogen treatment as the primary role of filtration is historic. Modern scientists look at biochemical interactions holistically and not in isolation. In wastewater treatment, the emphasis therefore is on lowering COD and you often find large filter beds because it is not as simple as just removing ammonia. This is the way people should now be thinking. All companies find it cheaper to sell something small. I cannot think of anything more boring than doing my phD on filtration and algae, but eventually somebody else will, and we will see a revolution in thinking as big as when EI first came out. Just think about how much things have changed in the last 20 years.
Filter capacity = essential. Flow control = essential.