Honestly, the stock design is pretty decent on these. The most common mod that people do is to turn the middle back chamber into a refugium. They use either a submersible LED or they put an LED on the outside of the tank shining into that compartment (use a razor blade and scrape off the paint to allow the light to go in). I've used both methods as well as just leaving it stock and I have to say that the refugium can be a PITA. If you go with chaeto and it breaks down, it gets caught in the return pump and is just more hassle than it's worth and if you use caulerpa, get ready for it to grow EVERYWHERE. I don't use the stock carbon filter. I use the small portion of ChemiPure Elite with some poly filter over the top of it in the middle chamber and call it a day. That combined with a weekly water change and it's good to go.
