How many fish?

[JumpingJellybeanz]

I've inherited a 125L tank which currently has one resident catfish. He's about 4 inches long and 9 years old.

I want to add some more fish but being a novice I think I'm in danger of putting too many in. Can someone with experience give me some advice? I was thinking of gradually adding:

1 clown loach
5 guppies
10 tetras

But I suspect that's too much. Yay or nay?

Really can't help with the stocking of fish but a good fish store can advice there. If you have a Madienhead Aquactics near you they are very knowledgeable. Avoid pets at home like the plague as they honestly haven't got a clue.

I keep guppies, cory cats and 2 clown loaches.

One thing I will say is the clown loaches are very boring we call them the grumpies as they don't like being looked at we can go a week without seeing them. I would not get them again.

Cory cats on the other hand are fantastic, really interesting and great to watch. Our pair are constantly playing.

Male guppies are beautiful but they don't live particularly long. Our oldest is 9months.

So far I've got:

1 bristlenosed pleco
3 platys (all male)
5 tiger barbs
+
10 cardinal tetras which are going back as they send the tiger barbs nutty. The woman in the shop said they'd be fine together. Clearly that is not the case.

I'm thinking of replacing them with either:
7 zebra danios
or
5 phantom tetras

Google tells me that both can live with tiger barbs ok but I'm worried that the barbs will go crackers again. Anyone have experience of these? What would you go for?