While cyclura take up to 5 years to reach maturity the iguana iguana usually reaches this in under 2 years...so it's safe to assume your ig is ready for the other supplement (in other words not a juvie).
You can, while you are using indoor lighting that are not high output bulbs, supplement with Ca/D3 a few times (like 3 meals) a week. If you use D3 at all, use the combination (I think reptical makes a combo Ca w/ D3), not the d3 that is sold alone---and never the drops at all. As soon as your ig is getting some nice outdoor time you can stop until the fall.
I really like this dust and can see the igs are actually eating more since I started using it....so far so good
How many lights do you have in your cage setup? Think about this fall perhaps getting one high output bulb (Trex spot) so all winter, when your ig cannot go outside, he will be exposed to wavelengths appropriate for iguanas
