Therefore, you'd better keep only 1-2 black goldfish in a tank of goldfish! Just match the goldfish with other colors!
If you want to raise fish according to feng shui, you can refer to:
1-2 black butterfly tail or dzi bead (for eyes) and celestial eye (for avoiding villains). If you like black, black goldfish can only account for one-third to one-half of the total number of goldfish. Too much is bad luck!
2-3 alternating gold plating or lanshou with white and red, (safe and smooth)
2-3 lion heads with gold or yellow and white or red and yellow, (lucky)
2-3 red hats or red tops (life is booming)
1-2 pieces of five-flower gold or extra-eye gold (this kind of gold is easy to raise and beautiful)
You have never raised or fed goldfish before. If the tank is big, I suggest you choose grass goldfish from koi fish or goldfish.
You can mix them freely, and you can ask me if you don't understand!
I hope my answer can help you!