I have both the side and bottom nipple waters.
The bottom nipple is the one made from an orange Igloo water can. It stays cleaner on the inside and mold doesn't seem to grow in it.
My white bucket with the side nipples will get very green on the inside. The water does stay cleaner but the green mold has to be cleaned out with a brush. I had to put a glass pie pan over the lid because the chickens would get on the top and poop would sometimes fall in the hole. I haven't found anything that doesn't need cleaning.
The bottom nipple is the one made from an orange Igloo water can. It stays cleaner on the inside and mold doesn't seem to grow in it.
My white bucket with the side nipples will get very green on the inside. The water does stay cleaner but the green mold has to be cleaned out with a brush. I had to put a glass pie pan over the lid because the chickens would get on the top and poop would sometimes fall in the hole. I haven't found anything that doesn't need cleaning.