and another blatant copy and paste-too tired to paraphrase
Wet skimmate is the thin light green tea-colored solution collected when lots of air and a relatively high water column height is adjusted for in skimmers that are adjustable (MR-2 type skimmers). This removes a lot of seawater and requires that any auto-top-off devices be turned off during such operations. Failure to do so may result in dilution of salinity. As an alternative (especially in sumpless systems), the system may be overfilled with seawater and skimmed down to normal levels.
Dry skimmate is the thick, concentrated skimmate collected when water column height is adjusted to about 3 or 5 cm below the collection neck (may be more or less depending on pump, skimmer brand, and venturi/air injection device) and the air injection is reduced to prevent excessive foam formation. This allows the skimmate to concentrate in the foam formed within the collection riser so that the skimmate collected in the cup is quite concentrated, relatively "drier" than the thin wet skimmate collected with less restrictive adjustments. This is usually the optimum setting for skimmers, as it does not remove large volumes of water while the system is unattended, yet effectively removes large amounts of DOC and particulates from the water column. This conservation of seawater helps to prevent fluctuations in salinity, especially in systems with automatic top off devices in operation.
Wet skimmate allows for better rapid collection of particulates and some organics, but at the cost of collecting extra water (around 2 to 3 gallons every 30 minutes to an hour, depending on the adjustment settings.) This extra water collected can be added to the total for discard from water changes, and acts to clear the water column of suspended detritus. This is especially helpful while performing detritus siphoning/uspension and algal scraping of the glass and when blowing the rock with current to remove detritus. You'll need to keep track of the total amount of seawater removed from the system, and replace that amount with fresh seawater to maintain salinity parameters. If you use auto-top off, make sure to adjust the height of the water in the sump before restarting the auto-top-off to prevent changes in your system's salinity
