We have always kept our operated and control animals separate, not because we know of any growth suppressing effects, but because it is (1) easier than sorting the animals out later and (2) our veterinarians consider it basic good animal husbandry, possibly reducing stress on the operated animals.

As much as possible, you should keep every animal separate from the others. Is there an effect of being kept together? You can never know. And a reviewer is right to wonder. Every animal kept with others is no longer an independent data point. So any statistical question is subject to suspicion, with good reason. Every tadpole affects the others that it is kept with. When in doubt, every tadpole goes in a separate container.