This is the image library of killi.net where images of killifish are stored, sorted in some reasonable order. Killifish are small egg laying tooth carps from tropical sub tropical streams and rivers and are commonly kept in home aquaria. Despite their relative scarcity in the pet shop, they have been an integral part of the aquarium hobby since the beginning of the 19th century.
These images are not in the public domain. But you can use them. Each image is copyrighted by the author and the copyright is part of each filename. But you can still use them. That's what they're here for.