Goliath Druid, earth companion question

[Mr.Kraken]

Hello to the playground. I am taking the Goliath Druid racial substitution levels from Races of Stone, and an issue has arisen regarding the Earth Companion alternative class feature. I am taking a 4th level animal companion (fleshraker dinosaur) which reduces my effective druid level regarding animal companions by 3. The Earth Companion, a feature I take at level 6, also reduces my effective druid level by 3. That means I'd have an effective druid level of 0. Does that mean I can't take the feature at level 6 or at all?

[eggynack]

Yeah, you need to wait until 7th, which means ditching the fleshraker, skipping the earth thing, or picking up natural bond or an equivalent thing.

[Mr.Kraken]

But, is it legal to take a class feature a level after the level you receive it?

[eggynack]

But, is it legal to take a class feature a level after the level you receive it?
No, but you don't have to. Once you have the ability, its actual use is strictly optional. You can make the trade at level six, and then make actual use of it at level seven.