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Wise decision to dump and fill. You won't have to do this every 30 days.
Have you read up on the likely causes of foaming? If you are using swimsuits in the tub, make sure that they don't go in the regular wash since they come out with detergent which then gets transferred to the tub. Also, the anti-foaming chemicals can cause other problems with your water and/or filters if you use too much. Some people dilute the stuff with water and keeping it in a spray bottle to use very sparingly when needed. Try searching for threads on foaming for more info.Good luck with the second fill!