Since coontail isn't commonly rooted, any fragments that are left behind following a mechanical/manual removal operation are free to grow. So, regrowth during the same season of such operations are common - and likely. To what degree? - it depends on many things. But, small to moderate population of coontail may actually be a desirable thing. But, if your pond offers a conducive environment, coontail can take over and become too abundant.
SONAR or AQUATHOL are two very effective treatments for coontail, with REWARD being a distant 3rd - but very suitable if your pond experiences frequent or constant flow-through.
SONAR, though easily applied, requires an extended contact-time (30 days+). Season-long control (or more) is normally obtained with one treatment.
AQUATHOL has more labor/equipment requirements, but contact-time requirement is much shorter than SONAR and visable results are quicker, and regrowth tends to be impeded to some degree.
REWARD works very fast but regrowth may occur almost immediately.
If you're avoiding herbicides for a specific reason or concern, that's fine. However, when properly employed, herbicides may provide a very cost-effective and environmentally friendly option to repeated manual-removal efforts.