My turtle has recently stopped eating lettuce. The weird thing is, he still gets excited by pellets, and eats them normally, swims around pretty normally (he likes resting alot), and would eat an apple (not a whole one of course
However, he seems to have gone off lettuce completely. He used to like it to the point where i could put in 1-2 leaves and it would be gone by the end of the day. Nowadays, he takes like 2 days to finish a quarter of a leaf and i have to take out the rest of the leaf on the 3rd day to prevent it from decomposing in the tank.
Admittedly i think there may have been a period where he would leave like half the leaf uneaten even after like 3 hours but in the morning it would still be gone. However, it has progressed, almost suddenly, to the point where he doesn't want to eat it at all (almost). The environment is pretty much the same: i've got a heater, same light etc.
I am worried that he isn't getting enough fibre, which can be seen from the fact that he is pooping less.
ideas: i moved about 3 months ago so maybe its something in the water thats finally taking effect?
I've also tried seeing if he would eat it if he was hungry but after 3 days of no pellets, he still wouldn't eat any lettuce so i stopped.
Has anyone experienced something like this? Any advice would be appreciated thanks.

