I use plastic perspex and drill my own holes in it so that you can drill holes to the size you want and as many as you want, also if ur breeding fish they can still see the fish on the other side of the perspex and that takes ther mind off of beating the kak out of each other. You can normally get massive sheets of clear, tinted or coloured from any DIY shop. To secure it i use rocks at the bottom and i sillicone metal loops/hooks that hook over the top of the tank then i suction cup them in place. Has worked really well for me with eartheaters and severums