I have a small pond, about 5 ft x 5 ft X 3 ft. The pump that came with the pond kit, Pennington InPond 600, doesn't seem to be doing a lot even though I have changed the filter pretty often since the pond being built last May. I also have a waterfall pump, Pond Boss Waterfall Pump 2000 GPH. The waterfall either has a leak or it splashes out the sides onto the rocks & I was having to refill water every evening. Sort of expensive because of the dechlorinator stuff. So I started turning the waterfall off at night & bought an aerator pump with two stones. I'm only using one stone right now.

The dozen or so goldfish are all about 5-6" long. Wondering if the waterfall pump alone for about 10 hours a day or so plus the aerator is enough to keep them healthy? I use a test kit to test the PH and it's been fine, well within the recommended range. The InPond pump didn't do much to keep algae down at all either & have to say I'm pretty disappointed in it. Just want to be sure I'm providing my fish with adequate care. TIA.

Your aeration and water mixing is very adequate for your current dozen goldfish. Nature's rule is " the fewer fish you have in the small pond the easier it will be to care for it and healthier everything will be. Your pond will over all be healthier if there were 5-7 fish instead of 12-14. InPond pump will not do hardly anything to help control algae. That is not how one controls algae - water mixing and aeration does not do it despite this as a common belief.
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Algae will flourish depending on how much you feed the fish and amount of manure they produce. More and larger fish = more manure = more algae = lower water quality. Fertility grows green water and string algae. Goldfish may eat some of the string algae depending on what type and flavor it is. String algae comes in lots of different types (genus species). Goldfish can be notorious for stirring up bottom sediments and causing filter clogging especially as they become more larger and more abundant. IMO the current pond conditions and inhabitants should do well until the goldfish reproduce, to cause numerous fish and then water quality will noticeably deteriorate. Then you will have problems and then know why, but until then with minimal additions of fish food things should remain relatively stable. Allow the fish to forage mostly on natural foods produced by the pond. If the fish always appear hungry and begging for food you likely have too many fish for this small pond.

In a small pond as this, my question would be, would plants help keep the nutrient level down and so the algae down? Same concept we use in larger ponds.

Yes - submerged vegetation and marginal plants growing in gravel filled containers will all absorb nutrients to compete with algae and help keep the water clear. Algae blooms occur because there are too many unused nutrients present. Sometimes planktonic algae is desired. It depends on ones goals.

Thanks all. I do have about half the pond covered with water lettuce plants & a few water hyacinths. Those multiply so fast I have to thrown some out every few days. I unplugged the InPond pump & pulled it out this morning. I don't think it's doing anything. When I first pulled it out I heard a clacking rattling noise from it but then that stopped. After reading up on it, I'm wondering if the impeller is broken.

If so I could order another impeller but honestly don't know if I want to mess with it if I don't need the pump to keep the water healthy. I do, as I said, have the Pond Boss Waterfall Pump going. Sorely tempted to take the InPond pump back to Lowe's where my son bought the kit. I'd have expected it to last more than 6 months or so.

If the water intake for the waterfall pump system is at or close to the bottom,,,, this and the waterfall currents are enough to fully circulate this 5x5x3 ft pond to maintain similar water quality throughout the pond. .