TArray allocator and memory pooling

Hi,
reading here : Optimizing TArray Usage for Performance - Unreal Engine

I learned about the ability to use a custom allocator for a TArray.

I have a TArray<FColor> of fixed size :

TArray<FColor> pixels;
pixels.Init(FColor(0, 0, 0, 255), fixedSize);

I would like to be able to reuse memory such that Init and FMemory::Free actually just flag in_use for a pre-allocated memory pool.
is there similar functionality in any UE4 allocators ?
any example code ?

Thanks,
Z