OK, I have always had a small (very small) pond everywhere I have lived. Always cobbled together without much planning or purchasing. I have a small pond here (110 g) that needs a water fall box/ filter. I am not going to try to make one. I found a small one online but the fitting says its 1.5 female. The pump I want to reuse has, I think a half inch male outlet. What do I need to buy to make this work correctly? I also need some tubing. I should know but I simply have never used this stuff before.
Is your pump going to be big enough for this box-filter? Half an inch to 1.5 inch is quite a step up so the waterfall flow may be a lot slower than you'd like.
I think the first thing to check is what kind of fitting is in the box - screw in I would assume but it could be a push on fitting (that you could also glue on for PVC pipe). Once you know what kind of fitting then you should be able to find a reducer at your local hardware store with a 1.5 inch male (screw in or push in) to a 0.5 inch male just like your pump (I am assuming this is a push on too with maybe a hose clamp of some kind). Now you just need ample length tubing that is 0.5 inch ID (inner diamter) to connect to the two half inch male connectors.
Usually pumps and filters for a pond that size, use 3/4 in to 1 inch fittings. Even the 1 inch is pretty intense. As long the water is allowed to just drop back in, and not used in a pressure filter or fountain (which can make the outflow intense) you may be ok. Lowes has a pond section outside in their garden department, and carries smaller home pond fittings, pumps, and hoses.