The bottom is covered with rocks that are anywhere from 3-4 inch to pea gravel size. It was washed gravel and mostly round rock, so I'm not sure I am understanding the "crystal" rock question. My water is basically clear other than the stuff laying in the bottom. I do have string algae in my falls that is dark green as well as some dark green algae by the old hand pump where the water hits the liner. No pea green soup. So I may need to move my water more? Like another pump? And another filter? Geez... light bill went up $90 last month. Not all from the pond of course but I sure dislike the idea of running anymore electricity. Pump is a Sunterra 4300gal/hr and is clean of debris, just hauled it out of the skimmer box yesterday and had a small leaf on the intake only. Skimmer has a leaf catching net and a blue mat filter for air conditioner I bought at Menards. I used a toilet brush to move the stuff around on the bottom to push it toward the skimmer but that could be a 4 hr job and then the next day it looks like I didn't do it. Am I expecting it too be too clean? If I leave it tho, it ends up with lots more on the bottom. I have 2 5" koi and about 12 3" feeder goldfish. I feed them rarely. Lots of mosquitoes here so should be plenty of larvae and other stuff to eat in the pond. What wiring should I check? The UV wiring all looks fine. Checked the transformer connections, etc.