| You are partly correct, a well kept fully grown discus should be 15-17cm in size, so your is half as big but it isn't fully grown. After the 9th month the discus will start to gain size sideways (get thicker) and becomes rounder, rather than getting bigger in diameter.
This is a growth rate guide by Hans, a true inspiration among discus keepers.
Approx. grow Stendker Discus:
2 ~ 2.5" 3 months
3 ~ 3.5" 4.5 months
4" 6 months
5" 9 months
6" 18 months
7"+ 24 months
Hans
An adult discus should be around 1-1.5 year of age. So yours is pretty young and still have a lot of growing to do. IMO you would need 12+ discus of the same size as in such a big tank as they would get lost, feels very insecure, can't find food and you are very likely to see deaths. Generally, for medium size tank (50-120G) people keep 1 discus per 10G, I have 9 in my 70G and I've known quite a few people that keep 15+ in a 120G. They REALLY need to be in a school large enough for them to see other discus wherever they are in the tank |