Right number of fish for tank

If it looks like too mutch fish it is. I have a 10 gal feeder tank and i'
keep 50 or so 1"gold fish in.operly Ichange water 2wise
a week and have great fillteration.

Even if the 1" per fish rule was correct you'd have to use the adult size, not the size of the fish right now.

You have to take into account the length, width and girth of the fish. I have a fantail goldfish that is 6 inches long 4 inches high and 2 inches wide. Would I count this as 6 inches of fish? No, more like 20 inches of fish counting the waste they produce.

So in theory, when stocking the tank take size of adult fish (LxWxG) + amount of waste to figure how many can fit. For bigger fish make sure you take into account the room needed for swimming and turning around.

No 1" per gallon isn't a good rule.

Its an OK rule for 2" fish, after that all bets are off. The 1" per gallon rule is an attempt to gauge waste by size. Fish get bigger in all directions, not just length: an 8" oscar is a whole lot bigger than 4 2" tetras. My 4" gourami is a bit more fish than all 6 of my 2" rasbora. So you can start at an inch per gallon but be realistic about making some necessary modifications.

Some fish are notoriously dirty (plecos, carnivores). Some fish are extremely active (danios). These all need to count extra in terms of waste produced.

Fish need space to move in. Some need running room. They all need room to turn around in. Even though a 55 is fairly long, its narrow: nothing that'll grow to more than 6"s belongs in there. Figure a fish needs at least twice its length to turnaround comfortably: this will get you towards the idea that clown loaches need at least a 75g, for instance: a 55 is just too narrow. Balas should have at least six feet in length to run in; giant danios should have running room as well.

Many fish are social and should be kept in groups. Some aren't and shouldn't.

Hopped up filtration does not increase stocking capacity.

Fish in a moderately or lightly stocked tank will be less stressed, more colorful, display more natural behavior, than fish in a crowded tank.

Cold water fish are a completely different animal and need a lot more water per unit of fish, marine fish even more.

Work out an idea of what you think you'd like to see and post back up here, folks can make some specific suggestions.

Unfortunately, or maybe fortunately, the guppies MAY eventually become dinner for the angel.

BTW You do know how large plecos get, yes?

There is no "rule" for how much fish you can keep. The one inch per gallon is given to new people for buying small common tetra's, guppies or other fish like that. Its just not true though. I would not keep ten of my one inch lemon tetras in a ten gallon tank, but I think 5 2 inch platies would be ok. A ten inch fish would obviously be a bad thing in a ten gallon tank.

Generally I go by the judgement, if its starting to look like it isn't under stocked anymore then its probably over stocked.