Thank you for the comment. My fuge, is really not much more than a ball of cheato and the one mangrove. I have no substrate except the detritus that accumulates although targeting sponges and tunicates is appealing.
Could you expand on the different functions performed by pellets vs. fuge. I like idea of carbon dosing you and Mcgyvr suggest and will consider. Thanks.
Comparing biopellets to a refugium is like comparing a lawnmower to a garage. The lawnmower just cuts your grass. The garage can hold things that cut your grass, or cars, or a workshop...
Chaeto takes light and nutrients (N, P, carbon in the form of CO2) out of the water and puts oxygen into the water, plus minor amounts of some organic compounds. Chaeto also acts as a great environment to grow all kinds of micro-life - pods, bacteria, micro brittle stars, etc.
Biopellet reactors hold biopellets. Biopellets serve us by acting as a passive form of carbon dosing. They put carbon into the water in a form that bacteria can easily use. The idea is that they fuel bacterial growth, and the bacteria consume nutrients,
In the end, both will lower nutrient levels, though by pretty different paths, and the Chaeto will give you a bunch of other potential functions, as well. The fact that Chaeto uses CO2 and releases oxygen means that while your 'fuge lights are on, it'll help stabilize pH (reducing CO2 in the water means you're pulling out carbonic acid and raising the pH). By running 'fuge lights on an opposite schedule from your display, you can balance out the pH over a full 24 hour day. There is an additional slight advantage in that the Chaeto is releasing oxygen into the water while the 'fuge lights are on. Carbon dosing, on the other hand, tends to have the opposite effect, since the bacteria it typically fuels are aerobic and consume oxygen.
If you're after nutrient reduction, both are OK as long as you understand how they work and how to manage them versus your tank conditions and your desired nutrient levels. The refugium gives you the other advantages I mentioned, though some of those can be had without the Chaeto, too. If you just fill it with rock rubble and leave the lights off, it'll slowly become overgrown with all kinds of non photosynthetic life (sponges, tunicates, worms, brittle stars, pods, etc.). That life can provide a minor nutrient reduction and water filtering capability (minor only due to the small size of the compartment), plus you're adding a ton od biodiversity to the tank, which is always good.
If I were in your shoes, I would step back and evaluate your needs and your goals. Do you actually have a nutrient problem? Do you have anything else you're trying to accomplish? Your 'fuge as it's set up now will give you some minor nutrient reduction and those other benefits. If it's not working for nutrient reduction, you can try liquid carbon dosing with little effort and without reconfiguring your system. Biopellets require a reactor, plumbing changes, etc. If you don't have a nutrient problem, I wouldn't carbon dose at all - it can be harmful to a tank that doesn't need it.
If you find you don't need the nutrient reduction of the Chaeto, but still want the biodiversity from a 'fuge, try the cryptic zone version (just take the light off and put some rock rubble in it.)
