ahel, Im not telling you what to do, but If I were you, I would consider at least some aragonite sand mixed in with the play sand if you still want to keep the play sand.
I was taught that the marine environment needs to draw from the aragonite to maintain some balances.
Another thing important to me is the refugium filter and a good skimmer.
Seems the refugium on a 24/7 lit cycle will keep your tank without pH swings and keep oxygen at saturation levels saving you from expensive pH buffers and sudden fish deaths. The skimmer will help remove wastes.
Try to find some good seeded live sand and macros to kick start your filter. If you don't find any, I will help you with some.
Salt water is not hard if you use common sense. There is a cycling period.
If your using artificial salts, read up on the toxicity of marine salts in the reefkeeping magazine right here at RC and make up your own mind.
Of course, this is only my oppinion and you can use this info anyway you like.