the size of the container can also be an issue in regards to temperature. Deeper is always better. I would also recommend at least bi-weekly water changes. Last summer I ended up with a big problem in my 70g container when I tried not changing the water for a while. Ultimately, It killed my pair of gold rams that had started breeding in there. My "pond" was heavily planted with a homemade filter.
Im cleaning it out now, I cant wait to get it back up.
