The exact same problem which we observed in Haji Anwar's setup in Dengkil. Because I've got no experience with gravel beds I could not say if sediments settling in them is a bad thing. Affnan would be the best candidate to answer that! For gutters types (nutrient film technique - NFT) however, sediment settling in them should be avoided at all cost. The reason being the fish matters will continually release ammonia in the gutters itself and it'll be all the plants are going to get. Since ammonia is alkali in nature, pH lockup will occur and make nutrients unavailable for the plants. I've also mentioned before that the trend around the world nowadays is to remove all sediments possible before flooding the AP system, the trend must not have occured without good reasons to do so.
Anyway, Andy quickly solved the sediment problem by constructing a RM 15 solution which is a vortex sediment tank from a small dustbin. You can see some sediments trapped in there. Periodically he will flush this tank and provide the nutrient elsewhere in is soil garden. They do make good natural fertilizers!
Some pictures to enjoy on Andy's test setup which employs rectangular PVC pipes (rainwater down pipe) from Arensi Marley Malaysia which costs RM 62 per piece for a 6-meter section. That is pretty cheap compared to using open top gutters! The only disadvantage I could think of is that the plant spacing is fixed as compared to using polystyrene suspenders which you can adjust by cutting new holes for a new spacing configuration. Nevertheless, it is a very good solution, and yeah they look good too!
Enjoy the photos below! I should be able to post some photos from the Dengkil setup in the next few weeks. Cheers!
The said rectangular pipes with holes cut in them. The size used is 120mm x 80mm
Seedlings look healthy although Andy is yet to throw some iron into his filters. Hope he's done that by this time...
Though his pond looked crystal clear, look at the pile of sediment inside this vortex settlement tank. Typically on a pond setup, this would be a prefilter before mechanical filtration. Bio filtration is usually set at the last stages of a pond filter. This gives me some idea on the setup I'm designing for my place.