Dear Mr Harris, 3.5 m² seem ... Published May 19, 2017 08:59 by Dr. Thomas Peters, Senior Technology Consultant at Dr.-Ing. Peters Consulting for Membrane Technology and Environmental Engineering Dear Mr Harris, 3.5 m² seem to be very small. Is it correct ? For big ponds exist chemical free, environmental sustainable solutions. Will be hapy to transmit a link. Contact us at dr.peters.consulting@t-online.de.