I used to connect my overflow coming from a tank to the overflow runner that goes to the sump but I dont anymore. It looks like you used 1.5" pvc for your overflow runner and 1.5" slip fitting by 3/4" FTP barb. Then you connected 3/4" barb to 3/4" barb with vinyl tubing. Instead of connecting them leave them unconnected. Add an extra 6" 1.5" pvc tubing on top of the 1.5" T from the runner and simply insert the 3/4" vinyl tubing. If you plumb it this way next time you will be able to simply lift off and remove each tank with no plumbing. This is how I build systems in our facility now. When I started I didnt consider the cleaning needs of mature broodstock system. Being able to more easily deconstruct a broodstock system will be something you will eventually appreciate. Cheers!