Well use intank on 50l and twin inline injectors with reactors on 500l.
Each have their pros and cons.
Intank great for ease and cheap but placement is critical and tank full of bubbles.
Inline work well and take the hardware out of tank and placement not critical but tank full of bubbles but plumbing easy and not expensive limited inpact of filter output.
Inline with reactors crystal clear tank placement irrelevant but more potential leaks and complex plumbing plus they can be noisy. Can also limit filter output and reduce the throughput in filter so less O2 getting to filter also.