I almost forgot... welcome to the saltwater world!
If you are using live rocks, there's no need to use dead prawns, the biological stuff in the LR will be enough. But I can see you're in the right track by dosing the good bacteria. May I know what's your current biological media? I hope they're not bio balls. Some may argue, but I go against them not because they're bad but rather too small in it's bio load capacity compare to more porous media (Bacteria King, BioHome, etc)
Diatoms are normal in the first few days of tank. So don't worry. Typically, they will show on rocks and sand... then those on rocks will disappear... then those on the sand. They will reappear every once in a while with phosphate, silicate, and nitrate spikes
Regarding nuance algae, well that surprise is still ahead of you (even on my tanks), but diligence and patience is key to prevent this.
About the aiptasia, don't just stand there and kill the buggers! (I hate them so much, sorry for the outburst)
Back to the dead prawn technique, the reason why I'm against this approach it's because it's an old technology and frankly obsolete. Before bacteria dosing was available, the only way to drive the cycle is to add something decaying in the tank and pray that the good bacteria dominates your tank and seed themselves on your media. But with all of the awesome progress with bio filtration technology, like Microbacter7 and the likes, there's no need for this old approach. Drastic increase of ammonia(coming from decaying stuff) may even back fire and even slowdown tank's cycle. You can ask around with some of fellow reefers here what's their experience with adding prawn(of course some maybe good, but there's a chance to be bad). Some will remember an early bacteria bloom and clouds the tank which some may argue is safe, but I don't think the same can be said by living organisms and nice critters on the live rock that you might want to retain. Just something to think about, living a dead fish to decay with a tank that cannot handle the bio load (like early cycle tanks), what happens?
In my experience, I kick started a few tanks already and cycling can be done within a week using purely dosing bacteria and LR.
IMO, you can remove the prawn and keep on dosing bacteria. You might consider dosing carbon source (Reef Fuel if your confident with Brightwell), but my advise you do this slowly.
Btw bro, you have the perfect substrate. And your lights are no less than awesome!