This is a follow up to my post found here: https://www.backyardchickens.com/t/1118478/keeping-duck-pond-water-clean-with-minimal-to-no-effort Ok, so it has been almost 3 months of the filter running. The water in the pond/pool has remained clear the entire time. Just have had to maintain topping it off and occasionally using a pool skimmer to collect larger debris (not absolutely necessary, but I do it anyway, not often, mostly to get feathers and leafs out). However, I have noticed 2.5 issues that will need to be addressed. These issues have not shown to prevent the system from working. Issue 1: MOSQUITOES!!!! The first issue is one I should have foreseen from the start. The water surface of the filter tank remains relatively stagnant, just enough to where mosquitoes can lay their eggs. The solution to this can be done in a cadre of ways. One is to increase the turbulence of the surface water. Another is to introduce fish that feed on the mosquitoes (not practical in the filter as the filter tank would be at "toxic" levels, the ducks keep the pond/pool water disturbed enough). Another is to screen the top of the filter so that sun light can get in but mosquitoes can't (this may prevent including plants in the system). And then there is Mosquito Dunks. I have chosen to get Mosquito Dunks. These are pretty cheap, about $1 - 1.5 a piece (come in packs of 6 at home depot, got 20 for $21 on Amazon). Simple to use, just drop the dunk in the tank and call it good. Should only take 2-3 dunks per season. Issue 2: Build up Out of curiosity, I decided to clean out the filter, especially since this design is not specifically designed to accommodate ducks, it was made for fish. So, I didn't do a thorough clean out, just a simple, basic one. Drained everything, sprayed things down without 100% disassembly, etc. To say the least there was a massive amount of buildup. However, I couldn't tell how much was the duck waste and how much was the bacteria and algae. In either case, it really didn't do anything to the performance as the water was still clean. To solve this, I am looking to introduce a pre-filter to the system. This pre-filter will be a mechanical filter, put in between the pump and the main filter tank (the current filter). I am thinking of 2 5-gallon buckets connected to the pump with a pvc T joint with 2 valves and then another T to the filter with 2 valves, somehow making it quick disconnect. This way, when one of the 5 gallon buckets fills up, then switch to the other and empty the waste out of that one. Another option to solve this is actually what I need to do anyway: enlarge the pond and include fish, plants, and other mechanisms of waste disposal. A larger pond would also afford the biofilter to be incorporated into the pond itself as it truly is in nature, which eliminates the need for a pump except to create water movement. I also currently have some ribbed tubing that I believe I should replace with something smooth as to provide less surface area for things to grow in the pipes and less places for waste to get stuck in the pipes. The trick will be finding something flexible, yet smooth of the correct size. A benefit that comes from the bucket system or the occasional cleaning of the filter: you get excellent fertilizer for your garden. Again the build-up has not shown to cause any problems as of yet. Issue 0.5: hyacinths As I stated in the other thread...hyacinths may not be the best plant for the biofilter. They grow so rapidly, I find they block the sun from penetrating into the filter. Not to mention how many I have had to throw out just to clear some room (though the ducks love to eat them, they go crazy for them). So again, I would recommend using a different plant, one that is less invasive. NOTE ON WINTER: As for what I will do for the winter, I have not figured that out yet. Though, this winter I believe I will be draining the system and restarting it in the spring. Especially since the only thing I can think of requires a 100% disassembly of the filter to install the heating element and then I have no idea how the waste will impact the heating element (I suspect nothing good, so I am not sure that is the best way to go). To make sure the ducks have water, I will be getting one of those heated pans and once or twice a day filling it up.