Yes, the seller is correct. It is a 200 litre tank.
It looks as though you have Malawi Cichlids in there. They 100% do need heated water, the temperature should be between 24c - 27c. When adding the heater, just increase the temperature slowly over a few days to the desired temperature.
In...
I have been busy behind the scenes. The tank is almost there now, just putting together the final finishing touches.
Recent additions to the tank:
15kg of dark Seiryu Rock
2 Custom Caves
2 Anubias Nana Paxing
1 Anubias Golden Nana
1 Anubias Barteri
1 Vallisneria Spiralis
On the technical...
I’d say it is too small for Malawi cichlids.
If you have soft water, you could consider keeping dwarf cichlids. Or if you have hard water check out shell dwellers from Lake Tanganyika.
If your filtration is ‘over powered’ for the size of your tank, which is what’s recommended for keeping African cichlids, I’d be comfortable with 30% - 50% water changes. Keep an eye on the nitrates and if they are higher that they should be, increase the water change %.
I’ve read on...
You'll certainly be looking to carry out 30%-50% water changes once a week to maintain good water quality. That's with very good filtration. If you're going for standard filtration for the size of the tank, then I'd recommend carrying out more frequent water changes.
It all depends on what fish...
Take a look at Cyprichromis leptosoma.
https://www.seriouslyfish.com/species/cyprichromis-leptosoma/
From what I've read it fits your profile perfectly.