THANK YOU for thinking of the health and happiness of your fish, and being honest about what you can manage. I wish more people would! (And yes, I do think there must be a fishy equivalent of "happiness" that they experience.) There are discussions all the time here about minimum gallons per koi to allow etc. and yes it may be true that you can technically keep them healthy with not a lot of space, if the filtration is adequate.... but I always wonder WHY BOTHER if there's not enough room for them to move freely. To see a group of koi moving together in a school across a large pond is an AMAZING sight. You don't see that when they are cramped. Without enough space they just kind of dart around aimlessly or don't move much at all. Which brings me to goldfish. There are some bred especially for ponds with bright colors and long fins - some look exactly like koi - only they stay small 10-12 inches maybe. You can get that same schooling behavior in a lot less space.

all my goldfish died this winter due to very cold snap pond froze over Iused the hose to keep water flowing. this was tap water .It worked last year but not this year was it possibly the cholrine in the water .

Depth will be two feet; I am not good as to the exact calculation of gallons but I am told that it will be pumping 4000 gallons of water within a certain period of time. I did mention that I am a newbie as you can tell by my response to that question. No rocks will be in the bottom. I don't know what you mean by a bottom drain. The pond has a liner. My local koi and goldfish supplier carries young koi about 4 inches long or longer. I will definitely start out with goldfish just until I learn how to keep the pond in good condition.

Consider doing some serious research. Asking people for opinions only gets you opinions which are almost 100% passed back and forth so many times people actually start to think they're facts. You're doing pretty good. You already understand no nitrite means no bacteria. You used the term "total ammonia" too which is good. You're already smarter than the average bear. Let's bump it up one more notch. Lets start with the easy stuff. You don't mention the temperature of the water but I have to assume it's pretty cold. Nitrifying bacteria slow down as the temp drops. At 39F they stop. At 46-50F they only work at 25%. So trying to get a bio filter going is a bit silly in most climates in winter. Moving the fish back to the pond has the same issue, no working bio filter. Moving them back to the pond must work cause that must be a safe place cause millions of ponds overwinter fish without loss. Must because of bio filter...right? Nope. A little harder now is the term "ammonia". When pond people talk about ammonia they almost always think of it a chemical. That's a problem. Ammonia in the pond is 2 chemicals, NH3 and NH4+. They're kind of the same, the difference is just ions. But ions are the thing doing the harm to fish so kind of important to us. What's an ion? Forget about it...not important to us. We only care about how to keep fish safe. There are lots of terms for NH3 such as "free ammonia", "Ammonium hydroxide" and probably what most people just call "ammonia". Let's make it simple and call it "deadly ammonia". This is really what scares us. Lots of terms for NH4+ too "ionized ammonia", "ammonium". Lets call this "safer ammonia" because for fish that's what it is, safe. Most tests are for "Total Ammonia" which of course is the total amount of deadly and safer ammonia. So a total ammonia test by themselves tells you almost nothing when ammonia is detected. There are test kits for telling the difference between deadly and safer ammonia but most people use total ammonia tests. This causes lots of fish deaths as people do all kinds of crazy stuff to lower ammonia...which may have been safe to begin with about now fish are stressed by the "fixes". The weird thing is deadly and safer ammonia go together. You always have both. And they change from one to the other in the blink of the eye as temperature and pH changes. As temp drops "deadly ammonia" converts to "safer ammonia". As pH drops same thing "deadly ammonia" converts to "safer ammonia". As temp and pH go up safer turns into deadly. You've been raising pH, or trying to keep it up, and have been cheered into doing so, to get a bio filter going which probably can't start due to low temps. Keeping the pH up is also busy converting safer ammonia to deadly ammonia. For example there will be about 90 times less deadly ammonia when pH is lower from 8.5 to 6.5 at 68F. By letting water temp fall and letting pH go down the fish can be safe even when total ammonia tests are crazy high. My suggestion is to find a ammonia - ammonium chart on the web you like and use that along with your pH test and water temp to determine first if you have a problem. It's likely you don't have a problem...but are doing things that could cause problems. If you have a problem then water change is the best option imo. Adding an ammonia binder means test results will be meaningless and you'll be flying blind. If needed water changes are often you could consider a 24/7 drip water change. Even with treated city water these can work. I also suggest letting water temp fall to around 40F. Converts most deadly ammonia into safer ammonia and almost stops Aeromonas bacteria from growing. I would not let water stay below say 37-39F for days. Lots of people with froze over ponds think the water temp is near 32F but that's another myth. Fish under ice in a backyard pond are likely enjoying a 39F temp. With an above ground tank the water temp can drop below 39F, even below 32F so you have to keep the temp up a little. Low temp also lowers fish metabolism which reduces ammonia production. Natural selection kind of worked this all out for us...as long as we don't "fix" it. I suggest letting pH fall to wherever it wants to be. You could force pH lower if you really wanted to, knew what you were doing, AND actually had a deadly ammonia issue AND water changes were a problem for some reason. Be really careful of people saying pH should be this or that range. They almost never know what they're talking about and are just repeating what they heard from other repeaters. In reality it's almost impossible for normal water sources to have deadly pH levels. Trying to push pH into some made up range with little understanding is more dangerous. Some other small points...size of the tank doesn't really matter. Sure, bigger the tank the slower ammonia becomes of problem...but it's likely to still be a problem. All the rules of thumb on ratio of water to number/size of fish is a bit silly. Just made up number out of thin air. Fish are kept safe with testing and understanding. Most city water now days don't use chlorine but instead uses chloramine. They sound the same so most people think they're the same and give the same advice they did 20 years ago for chlorine. Chloramine is made by adding ammonia. When we add chemicals to remove "chlorine" that ammonia is released which is why those pond products add an ammonia binder. And why total ammonia tests become useless even with temp & pH charts. Adding binders means you have no idea what's going on ammonia wise in the water unless you have specific tests for the binder.