Your Guppies
Hello Cor...
Ready or not, Guppy females can hold off on delivering the fry for some time until they feel conditions are right for fry survival. You can maintain the right conditions by keeping the tank water very clean. Work up to the point you change out half the tank water every few days and make the new, treated tap water a bit warmer than what's already there. Add some floating plants like Anacharis and Hornwort. These plants help keep the tank water cleaner between water changes and help the fish feel secure.
Clean water is the most important thing for a healthy fish. Do this, and you'll have fry in the tank.
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