Hi everyone....I am new to this and would like some help please. I moved into a property about 3 months ago which had a small pond in the back garden....approx size is 5ft x 3ft x 3ft. It had no filter, pump, or plants...just the liner in the ground and a dissused waterfall feature. The wife was keen to put fish in so we put in about 20 small goldfish that we purchased from a local dealer. I also added a pump (1000 lph) which i connected to the waterfall feature and also alternate sometimes by changing it to fountain. The pump does seem very underpowered as when i connect it to the waterfall it is more of a dribble at the bottom returning to the pond and we also leave the pump on 24/7. The fish have been fine for a couple of months, feeding well and seem healthy. However....now one or two of the fish have died and the others don't seem well at all.They seem to congregate at the top near the edge of the pond as if they are gasping for air....I know that sounds daft as they are fish and dont need air??? I would like to sort the problem out but don't know what to buy.....do I need a filter? Do I need a bigger pump? Do I need plants(I have none). I have added two treatments to the pond....both Tetra......one I add when I top up the water level with tap water which isn't very often.....and the other is an algae clear additive. I do live in the UK so temperature is dropping a bit now were approaching Winter....is that a factor? Any advise greatfully recieved... Regards Eddie