You have your first batch of tiny baby guppy fry, but they’re kind of beige and they don’t look very fancy at the moment. Not what you expected? Take heart, because they will begin to develop some color and character before long. There are even some things you can do to help them along.
One of the main factors that controls when guppies begin to show color is their genetics. If you have bred the same fish before, or some that are closely related, you can expect that this group of fry will start to show their colors at around the same age as the rest of the family. If you bought them directly from a breeder, ask him what to expect. Otherwise, you’ll just have to wait to find out. Typically, they will begin to get some color when they are between 1 week and 6 weeks old.
A guppy’s diet has a lot to do with how fast he matures, and the faster he grows the sooner he’ll get some color. Your guppies can live on nothing but dry, flaked commercial food, but chances are they’ll develop more slowly and take their time about showing you their colors. Give them a boost by adding live foods, such as daphnia, microworms and baby brine shrimp. Guppies are omnivorous, so they’ll benefit from veggies in their diet. Try giving them some cooked peas, but take the skin off the peas before you put them in the tank.
An overcrowded tank allows nitrates, one of the byproducts of fish waste, to build up. This will slow down your guppy babies’ growth, since a heavy concentration of nitrates is nature’s way of signaling that there are too many fish in the area. Too many fish means fewer available resources, so the babies grow slower so they don’t need as much. To get around this, remove half the water in your fry tank at least once a week, and replace it with fresh. This will allow your guppies to mature more quickly and show their colors sooner.
The temperature of the water impacts the metabolism of the inhabitants. Guppies can tolerate a fairly wide range of temperatures, but you shouldn't keep fry in a tank that is cooler than about 74 degrees. Warming the water up to 80 causes the fry to be more active, and you’ll notice they eat more as well. This results in babies that grow and mature faster, and end up getting their color sooner than they would in cooler water. When the water is warm, the babies will also benefit from more-frequent water changes, since they’re creating more waste.