I am new to this forum and have been growing annuals, vegetables and perennial seeds for many years. I invested in wire shelving racks and double 2 bulb fixtures over each shelf. The question I found not covered is the bottom heat issue. To germinate at a warm temperature I use regular heating pads...so much less expensive than heat mats. On low temp setting I can regulate the temp by using layers of toweling. Seeds that require warmth to germinate pop up in much shorter times than listed on seed packages. This will be my first attempt at starting new guinea impatiens..Divine series.