I assume you are talking about a standard srew in type compact flourescent? If so, most folks are having good results with them in the 3500-6500K color range seem to work best for macro. What is yours?
Tumbling is great if you have the sump space layout and flow available to you, but you can get by with any method that keeps detritus from settling in the plant's structure. It can be simple as using an upstream filter sock, just make sure you're switching it out every 2 or 3 days. A couple signs that your flow may be too low would be oily/foamy surface water and/or massive pod populations in the chaeto itself. Don't get me wrong, pods are great, you want as many as you can get, but they do produce a fair amount of waste irritants. When that detritus gets thick, it can block the light from reaching the middle and especially bottom layers. This is one reason that tumbling is an advantage. If you're going to do chaeto, you may want to have another dark area specifically for pods, and free of predators, and prefferably with some rock rubble. Pods like dark places, and they like rock piles, so they will naturally gravitate to those areas if you have them.
I had the same issue with my first couple attempts with chaeto in my sump. The first thing I did was to improve the lighting. Next, I used some eggcrate to keep the cheato from sinking to the bottom and getting sucked into the drain. As a happy coincidence, what ended up happening is now any detritus falls through and collects on the bottom, where light is dim. I can either clean it out, or stock the area with detrivores. In effect, I created a sort of benthic/cyryptic zone for beneficial filterers and detrivores. The starter culture of cheato I got from my LFS came with some hitchhikers...about halfdozen bristleworms, and a bunch of pods. Most of them have now moved downstairs. I'm thinking of adding some sponge encrusted rubble to that area, as well as more piers of eggcrate for sponges and tunicates to attach themselves to. Hope this helps!
