I can see a few potential issues with their setup. Aquarium cages can potentially cause issues. Birds are more sensitive to fumes in the air than other animals, and in an aquarium cage, the fumes would get trapped and concentrate. Tubs and such are often suggested for ducks and chickens, but it can cause a potential problem. Since they are going to quickly outgrow that cage anyway, I would think about another option. You especially wanted it set up so you can heat only part of the brooder so they can get away. An aquarium brooder is also going to trap that heat more.
Here is the brooder I use. There are a lot of threads on here where you should be able to get some other ideas for a brooder. I hear only one side of the cage. And one side is low so they can see out.
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Secondly, their water dish is not good for ducks. They sell them at TSC and other places making people think those waters are ok. Even I am guilty of buying one in the beginning. The best option for a waterer is cutting up a Tupperware container. You want a waterer they can dunk their head in so they can clean their nares and eyes. It is important for their health.
Here is my water container I use.
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I use a bigger one as they grow up, which is about a couple weeks later.
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