Do I need to pre-drill a hole if I will use bolts? Will the bolts split the 2x4?Not the best design given the weight of the tanks is sitting entirely on screws. If they shear you’re looking at a big puddle! This design can work for smaller tanks but still not ideal. Using dados to attach the cross beams will be a safer solution.
That said the design can work (I have used it) but I recommend using quality screws or even bolts (bolts being the stronger options). I used Timberlok screws which are designed to replace lag bolts/screws