Hi and welcome to the forum
Fancy goldfish (fantails, orandas, pearlscales, moors, etc) will be fine at 24C and so will the bristlenose. The fancy goldfish actually do better in warm water rather than very cold, so 24C is a good temperature for both species.
The big issue is the general hardness (GH) and pH of the water. Goldfish like water with a GH of at least 150ppm (preferably 200ppm+) and a pH above 7.0. Domesticated Bristlenose will be fine in similar water but if your pH or GH is too low, the goldfish won't do that well.
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Bristlenose are messy fish and so are goldfish.
How often do you do water changes and how much water do you change?
Do you use a gravel clean to remove the gunk from the substrate when you do a water change?
What sort of filter is on the tank and how often do you clean it, and how do you clean it?
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Goldfish need plant matter in their diet and so do Bristlenose. Duckweed is a good plant to grow for the goldfish but any soft leaf aquatic plant will do. Algae is good for the Bristlenose to graze on and it should have a piece of driftwood to chew on as well.
If you have a fluorescent light unit on the tank, replace the globe and starter every year. Use globes with a 6500K (K is for Kelvin) rating and have the light on for up to 16 hours a day. You want to encourage green algae on the glass for the catfish.
Most tanks only need 8-12 hours per day and your might be the same but start with 12 and see hour it goes. If you get lots of green algae on the glass that is fine. Use a clean soap free sponge or plastic scraper to remove the algae from the front glass and let the catfish eat the rest.
