I haven't had to clean my Apexi yet, but I just figured on cleaning the way I've used on other similar filters before.
Fill a bucket with warm water, add about 2 tsp of baby shampoo, submerge the filter and let it soak for a minute, then tap it againt the bottom of the bucket to knock free any trapped air and now let it sit for about 5 minutes.
After it's had time to soak, I grab the filter and while holding under the water quickly spin it back and forth (like a one hand steering wheel
). Bang it on the sides of the bucket occasionally to kick loos any trapped dirt.
Then just rinse it off VERY well and let it dry.
In alot of cases it's overkill though. But it's always worked great for me.