What is a filter sock and how to change it?
A filter sock is a fine mesh filter that removes any large detritus (non-living particulate organic matter) as water filters from the main tank to the sump. Andy custom made his own filter-sock holder using plexiglass and aquarium silicone and placed it in the drain to the sump. A hole is cut in the center of the plexiglass so the filter sock fits into the hole. Some aquarists have the filter sock at the very top of their sump. Ours, as you see, is several inches lower. This is because if there happens to be a backup in the filter sock, water will overflow into the sump, and not into the cabinet.
After adding the sand to the aquarium, the filter sock needed to be changed. It was so full it was causing the water to overflow into the sump.
When washing the filter sock, or anything for an aquarium, soap is strictly prohibited. On filter socks, you only use bleach and water. Most people do one or two cycles in the washing machine with bleach, a rinse cycle, and then stand them upside down to dry. From our reading, many people have a stock pile of socks and wash them when they have a large load. For now, we only have two socks and will change them as needed.
Filter socks come in different micron sizes. The higher the micron size, the longer you can go before needing to change the sock, but the less it will filter out. Most people change them every day, or every couple of days.