Hi and welcome to the forum
Can we get a picture of the entire tank so we can see ornaments, plants, etc?
What are the tank dimensions (length x width x height)?
What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).
Depending on what the GH of your water is, will determine what fish you should keep.
Angelfish, discus, most tetras, most barbs, Bettas, gouramis, rasbora, Corydoras and small species of suckermouth catfish all occur in soft water (GH below 150ppm) and a pH below 7.0.
Livebearers (guppies, platies, swordtails, mollies), rainbowfish and goldfish occur in medium hard water with a GH around 200-250ppm and a pH above 7.0.
If you have very hard water (GH above 300ppm) then look at African Rift Lake cichlids, or use distilled or reverse osmosis water to reduce the GH and keep fishes from softer water.
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My main concern is the 2 cichlids and the black widow/ skirt tetras. These tetras are renown fin nippers and need to be kept in groups of at least 10 or more. In fact most tetras need to be kept in large groups consisting of at least 10 individuals, this includes the bleeding hearts.
If the convict and firemouth do turn out to be female, they are less of an issue. If they turn into males, it could be an issue.
The female Betta won't like a big tank or an open tank. They prefer calm water with lots of floating plants and no big fish.
The clown pleco could get eaten or bashed by the cichlids.
The bristlenose catfish should be fine when it's grown but might be a snack for the cichlids, depending on how pleasant they are. Some firemouths are peaceful, some are awful. Female convicts can be the same, some are lovely natured and others are psychotic lunatics.
Make sure you have some driftwood in the tank for the bristlenose and clown plecos. Make sure there is algae growing on ornaments and glass for these fish too. You can leave the tank light on for up to 16 hours a day to encourage algae for them to feed on.
