Looking at the situation of this space, unless some accident causes all living beings within it to die out, given their food chain, which is similar to that of an ordinary lake, a little development would suffice for the space to have quite a number of inhabitants.
Although Zhou Tian had not had much interaction with the creatures of this space, it would be wrong to think there weren't many of them. After all, Zhou Tian hadn't been in this space for a long time. To say he understood it well would be nothing but a boast.
Especially since Zhou Tian, despite having fought several bouts here, had only been active within the same area. If it wasn't for the earlier need to throw off the Fire Fish by running for a while, he wouldn't have even left the territory he entered upon his arrival. Consequently, Zhou Tian hadn't thoroughly explored the space and couldn't possibly have a true understanding of it.
