silly skimmer :)

[fiorano]

i have an rs 135 and it seems to be doing a good job as long as i keep the water level high enough in the sump hahaha. but its been running for about 4 months now and now the water level in the sump barely makes it up into the narrow neck part it just sits there and fizzes in the main chamber... does anyone have any suggestions on how to fix this or does it just need a good cleaning maybe?