the LR is in a seperate sump. my blacktips dont like decor. i dont have a skimmer right now or uv im finishing up and a little short on cash. What kind of sharks do you have? If you can keep them in tanks than you shouldn't have any problems with a pond. Have you decided on a size? basicly my pond is a 10 Ft diamiter circle and 2foot deep, water is pumped from the pond to the filters than to the 100 gal sump full of LR than it goes through another filter(same as the first) than it is gravity feed back into the pond.