Hi there,
ignoring capacity for a moment, the only problem I see, is that although keyholes are generally placid, they still get territorial. I would be tempted to up the number of sterbais and pic smaller cichlids?
Just my opinion.
Keyholes will be fine not a problem at all one of the most peaceful cichlids around even for their size there are many smaller that are more aggressive. Even rams and apistos are more aggressive than keyholes.
Stock list looks fine though I would possibly up the number of cories to 6-8
Wills

is this stock list ok in a 180 litre tank??
(i do not have any of these fish yet i just like to plan ahead)
4 sterbai corys - Personally, I would increase this to 8-10, the more the merrier.
2 keyhole cichlids - Lovely, a great choice, I personally prefer dwarf cichlids like Cockatoo in which you can have a 1:2 ratio of M:F, but you've already said you wont change, so no worries
2 pearl gourami - Might want to increase to 3, just to make sure a male has more than one target.
10 neon tetras - Increase to 15 to get a really nice shoal
2 Bristlenose Plecs - Algae munchers.
is this stock list ok in a 180 litre tank??
(i do not have any of these fish yet i just like to plan ahead)
4 sterbai corys - Personally, I would increase this to 8-10, the more the merrier.
2 keyhole cichlids - Lovely, a great choice, I personally prefer dwarf cichlids like Cockatoo in which you can have a 1:2 ratio of M:F, but you've already said you wont change, so no worries
2 pearl gourami - Might want to increase to 3, just to make sure a male has more than one target.
10 neon tetras - Increase to 15 to get a really nice shoal
2 Bristlenose Plecs - Algae munchers.
You've got a nice big tank, might as well use it.![]()

I would be wary about two BN plecs ina 180 long term. Don't get me wrong, I love their quirkiness, but they do add quite a bioload...
If you want an algae eater, consider things like
- Otos (but give the tank several months to mature after cycling) - Lovely fish, but are really fragile these days due to the way they're farmed (dynamite). Can also be hard to find, not to mention expensive for a small group, let alone the large groups they ideally live in.
- Panda garras ( either do one or a trio, not two, as they can be territorially aggressive with each other... As I've found in my 240, the trio sometimes spark a chain reaction of "musical chairs" amongst themselves with then sometimes starts the Opsarius then playing up) - I cannot find these near me for love nor money, the nearest breeder to me is about 50 miles away and wants £10 per a garra, let alone panda garra. I can't really comment apart from the occasional aggression that you also commented on and perhaps price.
- Apple Snails? (no knowledge of these guys, but think I read they eat algae) - Lovely critters, I breed white ones myself. They do love algae, but you'd need a whole group of them to keep the waste and algae at bay.
- Florida Flagfish (but might be an issue with aggression shown to the Pearl Gouramis, or vice versa, needs someone else to step in here with experience) - American Flags can be very aggressive, especially the males. They also prefer cooler temps of around 22C and can't really be relied on to eat all the algae.
- Butterfly Goodeids (lovely, slightly less common livebearer. Males reach ~8cm, females ~12cm. Think it would need to at least be a trio with one male (bold yellow/black stripes on caudial fin). LFS would probably snap your hands off for the fry!) - Getting more and more common these days and are truly lovely fish, but again, you'd need a large group to keep algae under control, and I personally feel they might detract from the big shoal of neons.
- Hypoptopoma sp. plecs, which include the "Giant Otos" (although they are not of the same genus, reach ~4-7.5cm depending upon species, needs a group of 5+) - Lovely genus which is very closely relate to Bristlenose.