Yes and no.
The first catch of rainwater should not be used because it may contain a lot of “pollution” from the materials that have been deposited on your roof.
Water collected during subsequent rain periods would be pure and can be used for your fish without needing to use anti-chlorine. However, note that rain water will not contain any salts or buffers. So, depending on the water quality requirements (GH & KH), you may need to add aquarium salts.
Is rainwater good for my fish?
