Have a large water feature with about 100' of creeks, 2 waterfalls, 1 shallow small pond (40 sq. feet and less than 12" deep) and 1 large pond approx. 5,200 gallons (18' X 11' X 3.5' deep). Pump puts out about 2,600 GPH and draws from the bottom of the larger pond via a "criss-cross" pattern of PVC that is slotted (by a skill saw) part way through and covered with pea gravel.

Currently, I have to manually clean all creek bottoms "tilling" the gravel to remove algae, drain the ponds and pressure wash off the granite boulders that line the pond walls. This process is necessary 3-4 times annually.

Goal is to reduce this maintenance.

There are no fish (killed them with chemicals), water plants, skimmers, UV lights or filters (besides the "pea gravel filter") described. Water feature receives quite a bit of sun in the summer months. N. Washington state location.

What would you 'all suggest I do to reduce this maintenance?

Thanks everyone.