Whats in the goldfish pellets? Yellow labs, electric yellows..whatever you want to call them are herbivores. They rarely sell the proper food for them in any store. You will have to order food online for them. They are lake Malawi Mbunas.. a proper pellet will have spirulina and other veggies it. I reccomend making sure they are not full of fillers like wheat flour. They really enjoy fresh zucchini too! Cute it into spears then freeze them overnight and thaw it out and they will LOVE it. My mbunas go bananas for zucchini. You can even buy seaweed at an asian market and use an aquarium food clip and put that in there for them too.
If you have the time ( I don't) you can grate a bunch of veggies and add seaweed like peas, zucchini, carrots, spinach, and romaine lettuce. then freeze it in small bags with one feedings worth in each then thaw in tank water then give it to them