Hi everyone! My name is Gabe and I am living in North Carolina. I started in the aquarium hobby about 7 years ago and I love it and currently have a 55gl thriving tropical tank. We bought a house last year with the perfect spot for a garden pond, something I have always wanted. I was able to build it this year and I got it done about 8 weeks ago. I love it, but I am having some issues and I am hoping to get some help on here. The pond is oval, 8 feet long, shallow end is 6 feet wide and the deep end is 4 feet wide. The deep end is 24 inches and the shallow end is 16 inches with a shallower plant shelf. I calculated it to be roughly 200gl. The filter is a bucket filter that sits in the pond. At first it was just the foam that came with the pump filter and rocks sitting in a 12in square pot. After I accidently poisoned the fish now it is running with the addition of carbon. (explained further down) It started with two water irises, a pickerel rush, and 3 lilies. I added 2 more pickerel rushes because it was doing so well, Lucky bamboo cause I like how it looks but I have found conflicting opinions on if it is good for ponds. Just last night I added duckweed and two heads of water lettuce. All the planted plants are in clay pots with a bacteria rich aquarium soil. The plants are doing great and the irises are blooming. I live in planting zone 8. After a week, I added 4 small koi. They seemed to be doing great so I added 2 more 2 weeks later and that was going to be the only fish. They were doing well but I was having some major water issues. I tried Algeacide and this product that is supposed to clear the water and nothing worked. I nearly emptied the pond after 2 weeks of having the fish and scrubbed the sides with a towel and that helped until the algae grew back. The pond sits where it gets at least 6-7hours of sun off and on throughout the day so I know that has to be part of it. We went away for a week and when we got back the water was completely green so I couldn't even see to the bottom of the plant shelf and the filter was so clogged it was barely spitting water. So I drained the water down to the deep end. The fish were fine and very actively swimming away. I cleaned the pond liner with what I thought was a clean towel. I tried a new algae killer called Pond and Fountain Cleaner Tablets from Naturals. All the chemicals I was using in the pond says fish safe. So I filled the pond making sure I added the dechlorinater just like last time. Well I must have used a towel with soap on it because in 3 days all the fish were dead. I tried to save the last two by keeping them in a clean bucket of water and completely draining the pond and filling it with clean water but they died too. I am not going to add anymore fish until I am sure the water is clean and I have the algae issue better controlled. So now the pond has been going without fish for a little over a week with carbon in the filter and the water just gets greener everyday. Today I can barely see through it but the filter is not clogged at all so progress? I just bought a test kit and the readings are Ammonia 0, nitrite 0, phosphates 1ppm, pH 7.5. There was no Nitrate test in the Master Pond Kit. My hardness is in the medium range. My questions are how long should I wait to put fish in and how many do you think my pond can support? I did my research but some stuff is so vague and I got a trial and error vibe from a lot of what I read and saw on videos. I was thinking a month and only 2 fish this year. What else can I do to control the algae? UV filters are expensive which I am willing to spend the money but do they actually work? Should I do water changes and how much and how often? I swear I read that you don't need to with ponds but now I think that was wrong. I have gotten advise from several people including the people at Upscale Aquatics, a local aquarium store that I could put a common pleco in to control the algae. That seems wrong to me. Would it survive my winters and is my pond big enough to support it? And also, can I put a locally caught crayfish in my pond? Any help would be greatly appreciated.