I have had my small container pond (60 gal) for a year and half. I have 5 pet store goldfish we bought last summer who are still around, and lots of snails to help with the algae. I only have water lettuce, my dog takes plants out looking for frogs. We recently cleaned out the pond d/t a lot of build up on bottom. 100% water change (a lot of what I'm reading says not to, but we have done it before without issues) and a good filter cleaning. After this last time I noticed the water getting hazy, and I think it smells like something died. Any ideas? I'm starting with 1/4 water changes for a few days.