Eheim used to make a prefilter that went on the end of the intake tube that held a good amount of course filter material. It was about 2-3" around and deep and took a long time to clog. Don't know if it's still available. You could also adapt an internal filter [their available as an accessory for hagen powerheads] to your intake. You may have to try different filter media to work right with your setup. It would increase you main filter's media life also.

James
Thanks for the idea but I only run 10 inches of water in the 75 and the intake is located in a cave at the back of the tank. Would be very hard to get to. I think what i might do is use some filter floss right above the impeller chamber. Hopefully that will catch the sand before it gets into the lower casing?? It took almost 7 years to rub the hole in it lol. Anyway, thanks again for the tips ,may check them out if i find anymore sand in the chamber.
gary