Green algae in new marine tank

[Rhys23]

Hey guys, I'm new to the whole saltwater setup thing so I apologise in advance for any silly questions I may ask!
I recently purchased a new 25 gallon marine tank and with an inbuilt filtration system. I'm looking to eventually setup a fish and reef system but for the time being I am just trying to get through the first cycle. I set the tank up three weeks ago and it currently holds one piece of live rock and two pieces of dead rock with crushed coral substrate. after the first week diatoms arrived and about a week later it disappeared and now the tank is covered in green algae (there's even algae particles floating on top of the water. Is there anything I can do to get rid of the problem or does it just disappear by itself??
I did a 30% water change last week and bought a cleaner snail but that hasnt really helped at all. Any help or support would be greatly appreciated!
I tested the water today and these were the results I got.
Ph: 8.1
Ammonia: 4.0ppm
Nitrites: 5.0ppm
Nitrates: 5.0ppm
Salinity: 1.027

 

[Rhys23]

Just some pics of the tanks progression so far

 

[Bectan01]

Still in the middle of your cycle so I wouldn't worry too much just yet. Good idea to keep testing until you see 0 amm and nitrite. Did you add an ammonia source? Ordinarily there is no need for water changes during the cycle but your little snail might not make it through at the end you will see high nitrates and that's when it's time for a big water change and livestock! What's your initial plans for the tank?

 

[Rhys23]

Okay, I used the live rock to start the ammonia cycle.
I'm thinking of just getting a pair of clown fish to start with and then look into getting corals further down the track, I don't really want to rush everything being new to the saltwater side of things and all.