The location it's in it only get about 2-3 hours of sun so I didn't think a shade cloth would be worth itThere's your problem. Pond that small Is hard to balance. If it is shallow algae will take over. Try a shade cloth over the pond.
Are they suitable for outdoors in the uk because it is coldwaterAmerican flagfish eat any algae. Rosy barbs also will eat string algae.