The plumbing hardware on aquarium overflow setups is very susceptible to salt creep buildup. The equipment is often located in an area of significant water splashing, and the left behind salt can block the air inlet on the drain line. This buildup can cause a very loud gurgling noise, which is obviously not conducive to a peaceful aquarium environment, but it can also be far more troublesome than a little noise. If the drain is plugged and the return pump is still moving water, the aquarium could overflow. To prevent this, many aquarium keepers utilize emergency drains, which are often set at a high level than the primary drain.
