Alright, I think I'm in over my head this time.

I've been wanting a pond for years and finally decided to put one in this year. It is in a raised bed set against my foundation with two open pools at the lowest elevation. There are two raised bog areas as natural filters, plus a stream bed, a waterfall spillway, and a rock pool for movement and airation. I chose to landscape it naturally with stone and native plants. Overall, I am guessing it is only about 700 gallons total.

My driving force to complete the project finally were the four 4" koi that I purchased for my birthday in April. There are 3 basic koi (Fire, Storm, & Thunder) and 1 butterfly koi (Lightening). They are now about 8" long and happily living in my pond area with my 2 adopted frogs.

My problem is that I suddenly have had baby fish appear in the pool that I have no koi in. Granted, my filtration system exchanges water between both pools and bogs, so I suppose the babies or eggs could have been sucked up and redeposited by the filtration. The real perplexing thing is that I thought koi could not breed until they were 2 yrs old. I also tossed around the idea of eggs attached to my water plants when I bought them, but I stripped all the soil from them, throughly washed them under pressure with my hose, and repotted them in straight pea gravel (plus I bought them where I work as seasonal clearance items after they had already sat around for several months).

Most of the fish are very small and about the size of small guppies, but one is actually about 1 1/2" long. I can see that some of the babies appear orangeish and others are white. Some are solid and some appear to be developing dark patches on their bodies and/or fins. From the looks of the biggest one I am assuming that they will be either koi or comets.

Winter will be coming soon here in upstate NY and I have an air pump and 2 heaters (in case one malfunctions) that I will be placing in the larger pool. Then, I will be draining the rest of the system until spring. I am afraid that the baby fish won't survive the winter, so I have been skimming out the mystery fish as I see them and putting them in my guppy tank for now. The unheated tank has live plants in it and they seem to be getting along quite well in there so far. I know I will need to move them as they grow larger, but it works for now.

Does anyone have some helpful input for me in this matter? At this point, I think I could use a lot.