Probably fine with the Brightwell then as the Maxspec are considerably stronger unless space is an issue. The two pack is meant for 350 gallons, I use 3 in my 265 barebottom since no sand. They are about the size of a post it note pad vs the size of a large brick and one of the reasons I prefer them. The other being the brightwell start to melt over time, the lower the ph the faster it melts, and I had an Aluminum problem once when one turned to dust on me in the sump. Keep a steady Ph of 8-8.3 and they last multiple years with little issues though.