Hey there, Lori. I don't blame you for feeling overwhelmed. The last owner really should have left instructions.

If the pond is the size you are guessing then 10 Koi would have been far too many. A 5x4 pond is only 588 gallons. With a lot of extra oxygen and circulation you could have maybe three smaller koi but allowing for growth even two would be a lot. Goldfish or comets don't get as large but certainly 4 to 6 would be enough. Why don't you measure the pond again to make sure of it's size. There are formulas to figure out how many inches of fish a pond can support.

We could use some more details such as filtration, pumps and bubblers available. Do you have a liner, what kind? Happy ponding.

You didn't say anything about a pump and filter. Do you have them or did the previous owners take them? If the pond was that dirty, don't blame yourself for the fish death. The previous owners killed them.

That's a great size for a goldfish pond. Get your pump and filter running for a while until the water is looking clean. Get a test kit that allows you to test pH, ammonia, and nitrite at a minimum. If your tests show the water is good, get 2 or 3 little goldfish and try them in the pond. After three weeks if the chemical tests are good and your fish are doing well, you can add another fish.

Ideal stocking for your pond is ~5 goldfish. The fewer fish the less work in maintaining them. Those little inch long fish will be 5 or 6 inches next year, and will double that size before they are done growing. If you plan on 5 fish, you will probably be able to hold the number down to ten, and that's a workable number for your pond, just more cleaning and water changes. There's always another fish that you would love to have in your pond.

Thanks so much for the help!! There is a pump, filter and something else (it's supposed to help keep the water clean). We have filled it and have a small waterfall going. I bought some treatment stuff today and put it in today too. I'm hoping that in the next 2 or 3 days we can maybe get some fish.... can't wait!! I will keep everyone posted and maybe with a picture or two.

If you haven't filled it back up again, you can get a better idea of the number of gallons if you check the water meter in your front yard both before and after filling, and do the math. Just don't run a washing machine or flush the toilet during that time, or it'll give you a false reading.

I concur that goldfish are a better fit for your pond than koi. I have seen koi in very small ponds, but they're more difficult to maintain and keep healthy.

Don't put in fish until you have tested the water! Give the filter a few days. I said to get some little fish because they are cheap and adaptable, but give them a chance.

You are going to be far better off with goldfish than with koi. Koi require much more care because they produce much more waste than goldies. Koi are fun but they are poop machines and foul their water very quickly. Goldies are 100 times easier.

I would clean out everything thoroughly and start fresh. If your source water contains chlorine or chloramines, you will need to add dechlorinator to the water before you add fish.

A "stock tank heater" can keep a small hole in the ice over winter. This will keep gases from forming under the ice that can kill the fish.

Tank heaters are expensive to run. I have 3 Ponds and all I run in winter is an air pump, set 12" below the water surface.
I also cover it in winter to keep out the leaves and such that blows around in winter storms. Clean it and reduce the number of fish or get smaller ones. I also recommend a UV light, This will get rid of the green algae the mucks up the water. Please if you have any more Questions or if I can help in any way email me I will help all I can. Every pond experience should be a good on, Frustration because of lack of knowledge can ruin that pleasure.

Here is a link that might be useful: My Gallery

That pond is far too small for even one koi let alone ten. Not your fault they died.

Please wait to put goldfish in the pond.

Since you drained it and scrubbed it, it is likely going to go through a green water cycle. This is normal.

Add plants and let the water cycle before adding fish.

Thank you everyone for all your help. You have all been so helpful and I am taking in every bit of advise I get. I just wanted to update everyone on where my pond now stands......
As I mentioned, we drained it completely, hosed down the walls a bit (there was still a little bit of algae though)We re-filled it and treated it with a water conditioner and also this "sludge" remover stuff that we bought. We went to an Aquarium store and spoke to the people there who gave us suggestions and told us to bring a water sample in. We did that today and as it turns out, our water is very good he said. ??? I didn't think it was because it's still kind of dark. To me, it's still a bit brown but he said it is ready for fish. We also found out from him based on the dimensions that it is approx. 900 gallons!! We looked at Koi while we were there but decided on goldfish for now. We may add a 2 or 3 koi later but so far we have decided on goldfish. Today we bought 10 feeder fish. We got home, floated the bag for 45 minutes or so and away they went......... RIGHT TO THE BOTTOM OF THE POND!!! Or, at least we think that's where they went. I know the water is kinda cold still but we'll see how they do. I don't know if they are cold, scared or what but we can't see them. This brings me to my next question for all you wonderful pond people! We can only see about a foot down. The liner is black so I know it won't be "bright" but how can we make the water even clearer? Any suggestions. I'd love (in the perfect pond world) to be able to see at least half way down? Is that even a possibility? Like I've mentioned before, I really have no clue. I will say though, we are getting really excited about our pond. We even leave our window open at night because we can hear the water running... so exciting. Ok, so I'm a geek!! lol

Ok, so I just checked on the fish (again) and they seem to swimming around a bit but are still kind of grouping together in one corner. I guess they'll get used to it?? I sure hope so.

LOL! Going to the bottom is normal behavior for fish that are in a panic. Sometimes they disappear for weeks. They may even temporarily lose all their colors.

The dark color of the water is probably tannins but it is also possible there is debris in the water. To figure out which, scoop some water into a glass jar and let it sit undisturbed for a couple of hours. Any debris or free floating algae will settle out or float to the top. Tea colored water shows there are tannins or other organic compounds present. Some of the organic compounds are harmful to the fish.

Tannins come from rotting leaves, peat moss in potting soil and any thing else organic that is rotting. It often has an odor like sewage that is unpleasant.

Adequate filtration will eventually remove debris and some of the algae. To get rid of the rest of the algae you can use chemicals or a UV light. I like the UV since there has less chance to harm the fish and it doesn't bother the algae that grows on the sides of the pond. That is considered beneficial and the fish will graze on it. The UV can also kill some free floating parasites that show up every so often. I have never had the problem of green water.

For tannins (tea colored water or tannic acid) you need Activated Carbon also known as Activated charcoal placed in a permeable bag in a place where there is an active water flow. The tannin molecules react and combine with the carbon molecules on the surface of the chunks. Odors in the water are also removed with AC. Zeolite will handle most other organic compounds. There are chemicals available for this but there is a chance they won't work as well. Try the Zeolite. You should test the water for nitrates and nitrites (organic compounds)regularly.

The black liner is the best color to have. The colors of the fish pop out when you see them, so long as the water is clear. You will be able to see all the way to the bottom.

Has anyone suggested you get a Pond Test Kit? It is an important thing to have. Did you remeasure the dimensions of the pond to get the volume of water? I used two sites to get the 588 gallon measurement.

I can't hear the pond inside of the house. I have been looking for an inside-outside intercom to take care of that problem. The sound is one of the best things about the pond. I guess I must be a geek too.

Please do not put any koi in that pond. Most experts consider 1500 gallons a minimum for one koi...they require far more filtration and work than goldfish too.

Ten goldfish are going to breed and you'll have thirty next year.

Aquarium store employees may not be knowledgeable about pond cycles. It may have tested fine for fish but it still will likely go through a green cycle where you can't see them and when the oxygen levels would be low. Always better to wait and add plants and let ponds cycle before adding fish.

Fish cluster together and hide at the bottom when they don't feel secure. You've got open water with no cover from aerial predators.