We have been using chaeto for many years in a refugium. For us, the finer strain mats-up, breaks-up and collects detritus, but grows quickly. Chaeto not only looks cool, but it successfully outcompetes algae for nitrates. If you plan to keep chaeto in your sump underneath the tank, invest in a small red LED grow light to clamp onto your sump to help the chaeto grow. If you really want to get fancy, you can also install a small powerhead in your sump to keep the chaeto spinning which clumps it in a nice round ball. The movement also makes it less likely that detritus gets caught in the chaeto.