I agree with Adam.
How do public aquariums deal with 100's of fish crowded into a huge tank? They feed a ton and filter like crazy. They don't leave filtration to just biological filtration. I have noticed that Blue Hippo Tangs in a public aquarium are as fat as 2x4's.
You don't have to be a public aquarium or have a bucket of cash to filter like crazy, you can do it in a different way.
Biofiltration can be doubled, even quadrupled, without having to add equipment or a lot of established LR and LS. How? Add a large amount of Macroalgae to the display tank and a large amount of Macroalgae to a Refugium that is lighted 24/7. Then start feeding all that the new fish need. The fish will learn that there is plenty of food (aggression is 90% caused by the perception that there is not enough food).
The large amount of Macroalgae will do three things:
1. Eat/reduce pollution like crazy;
2. Provide food for the fish; and
3. Provide cover for the fish
Finding a large amount of Macroalgae is not that difficult. People here are harvesting from their Refugiums all the time. A small amount of Macro can be grown into a large amount in as little
as a month by feeding it fish food and making sure it has plenty of good light.
As time goes by, the algae will be eaten, or can be harvested, allowing bacteria, bug and worm populations to increase, thus handling more and more of the biofiltration. After a couple months, the extra Macroalgae can gradually disappear as a food source, being replaced by food such as lettuce and Nori.
The power of algae to clean pollutants out of the water is sometimes misunderstood in this hobby. What I have described here really works well. I have done it dozens of times.