I posted somewhere how I did it. Thought it was here, sorry. Might have been in a thread about the fans.
First, I modified the mount by taking a piece of acrylic and cutting an opening that I originally slide the stock fans into.. This helped with the noise that is caused when the fans are shoved into the opening in the hood. I read somewhere tha the noise is caused by the beads rubbing the case. I held the new mount to the back of the hood with 3M command stripes.
These new fans have their own power supply and are not hooked up to the tank. They also have a speed adjustment that comes with it. I used small nylon cable ties and hooked the fans together. I also use the small cable ties to attach the fans to the mount that I had made to hold the old fans. Since the ends of the mount have command strips on them, I attached the cable ties to the top and bottom of the frame. Since the ties are small, they are thin and do not interfere with the command strips on the end attaching. The only down side is that they are really thick fans and so if I need to place the top all the want up, I have to pull the fans assembly that I have built loose. Since I am using command strips, this is easy.mi just press them back in place when I am done.
To answer your question about the moisture. I didn't have a moisture problem when I ran the stock water coloring fan, but even though the mount helped with the noise, the stock fans eventually start to vibrate. So far these new fans are quieter than the stock ones ever were and give off more air. I am convinced that the inside of the hood is drier and that they are keeping it cooler and my rate of evaporation seems to have increased. I actually have unplugged my chiller, it tends to run more in the winter because the house stays warmer than it does I the summer. The tank has not gotten over 78.5. We will see what happens this weekend, it is supposed to get cold again and I haven't got to see what happens when ther is a fire in the fireplace.
If you click on the Amazon link, you will see that you can get these fans in several models. I bought the double. They fill the space that I cut out in the mount almost exactly like the stock fan did. The fans came with metal guards to screw on them. I did not attach that to the side that is towards the tank, but I did attach them to the side that is on the outside. I then used a wire tie off a bred bag to hold the original power cord for the stock fan out of the way and to prevent it from falling into the blades of the new fan. Since we damaged this wire and I have removed the fuse, I may cut this wire off totally to get it out of the way.