There are five main types of fish sold as gold nuggets, which implies black fish , white dots and white seams to dorsal and caudal fins. There's a normal, small spot, large spot, and yellow and cream spot 'flavours' but all are similar. I have a nice 'normal' one in a tank with a 5 inch L-33, black base with white spots.
The first source you should try is planetcatfish.com, which has the gold nugget as a catfish of the month, and will tell you max sizes and so on. If you look in the forums you'll also see a lot of people reckon this fish is not the easiest to keep, but there are basic rules you must stick too. Even then small, recently imported Baryancistrus are not the strongest.
Gold nuggets need good , clean , well oxygenated water. Get some water flow moving in your tank - I have approx 1000 litres an hour in a 200 litre tank where mine live and that seems ok. Note that every time these fish are bred though, and it's not super impossible, people are really pushing the water around - they need that oxygen, especially as they prefer temperatures around 78 - 80. Don't worry about pH within reasonable limits, but get used to water changes, the more the merrier. 10% once a week is the absolute base limit, 10% three times a week and your nuggets will thank you. This is partially because of their feeding habits.
I've seen reports of Baryancistrus chewing plants, but I've never seen this, though honestly I don't really look. I also don't expect nuggets to clean algae - they spend most of their time browsing the substrate in the wild, eating any organics they find, small shrimps. I feed mins shrimp, catfish pellets and the like and they tuck into those pretty hungrily as well as just trundling around chewing the gravel and any surfaces. To give them ample food, you effectively need to overfeed to keep food lying around for them. I feel, that like marine tangs or angels, they need lots of small meals, not one or two big ones though mine punce on bigger meals atastonishing speed. Thus you need to do the water changes described above, to keep the water aadequately clean. Like other peple, I suspect the vast majority of these fish don't grow because they're slowly starving to death. If they're eating algae it probably means there's nothing better for them.
Yes they are bred. And yes, I think they're absolutely beautiful. Stick to some simple rules, and they really are great to keep, and soon start to come and feed and be out during the day.
