He said that they move so slowly and it would not be possible for them to control the pod population. Do they effect the sand bed so that the pods won't multiply or do they simply ingest the pods?
I too, am no expert, but, if your tank is big enough, 1 prolly wouldn't eat all of the pods. In a 75, i'd say it's just a matter of time before their all gone. If you had 1 in a 6 foot tank, the pods would prolly keep up.(just don't get a mandarin)