i have a murray river shortneck turtle, i heard they grow to around 25 cm, mine started at 4 cm and ive had him for 3 and a half months and he now has a shell diameter of around 7.5-8cm, is this normal
They basically keep growing for many years. The more you feed, the faster they grow though not necessarily larger. Fast growth is usually at a cost to something. Eventual size, bone and shell density or even longevity.