Hello and welcome, Diva! I'm sorry no one has answered yet -- we're usually an active group that jumps on every post. And where are you located, BTW?
I'm probably not the best one to help you, but will do my best. You asked for equipment recommendations, but not knowing your experience level, hope I'm covering what you want to know and not going overboard. In gerneral, you're going to need a pump and a filter, but I'm not going to try to recommend brands or types.
- Can you post a picture of your set-up? [or a link -- I looked preforms up on the LOWE'S site, but what they offer now may not be what you have]. This is a small pond, so if will be helpful if we can see what you're dealing with and what your plans are.
- PUMP: You want to circulate your water about 1-1/2 times per hour, and that's usually how you figure out your pump size. Most people tend to get a pump that's larger than what they need.
- FILTER: There are so many types of filters....and filter set-ups. We have some members here with small ponds, so maybe they will see this and give some input for you. A lot of us use DIY filters and it would [it seems to me] be easy to customize something to suit your needs.
- A water test kit [this is a must, especially with a smaller pond!]! You'll want to monitor your ammonia, nitrite, nitrate, and pH levels. The "drop" tests are more reliable than the "strip" tests. If you don't already know about it, please read up on the nitrogen cycle.
- Are you going to sink the pond in-ground or have it above-ground? Which ever you choose, be sure it's going to be easy for you to get to it for maintenance [and to play around with ] -- if it's a pain to get to..... [speaking from experience].
- If you sink it in-ground, be sure that the edge is above the level of your yard -- otherwise you might get run-off from your yard going into the pond.
- Where will you locate your pond? A pond this small is likely to overheat if you place it in full sun.
- Depending on your water source [well vs city], you may need to add chemicals to neutralize chlorine and/or chloramine -- this will be added every time you add water or do a water change. It's a good idea to have extra on hand -- for water-loss emergencies [again, speaking from experience]. Water-loss [or over-fill such as leaving water running...] emergencies are going to happen.
- Are you going to have any plants? Not only are they pretty, but they give the fish a place to hide as well as keep the water cool during warmer months. And they can help with water quality.
- And if you live in an area with cold winters, you need to consider what you'll do with the fish when the temps drop. If the frogs are native, free-roaming, they can take care of themselves.
- Here's a helpful link: http://www.your-garden-ponds-center.com/fish-load-calculator.html It's a "fish load calculator." One of the biggest problems people seem to have is over-stocking their pond. Too many fish [or large fish] will lead to water quality problems, which will lead to sick fish. Those small goldfish are going to get bigger [and might have babies]. Any change to your system's balance is going to have an effect on the water quality. And keep in mind that "clear water" doesn't mean healthy water. See note about test kits.
Hope this helps!