Good luck on your mixed reef, possibly the most difficult of tank styles to get right. And it is difficult for several reasons, with lighting being just one. SPS works best with a par range around 250 to 350 PAR, LPS typically happy between 100 to 175 and sorties below 125. This range of lighting needs are typically solved by layering your corals with the SPS up high on the rockscape and the LPS towards the bottom with the softies strategically placed. Now to achieve a good spread of light across your 40 inches of tank is going to be a challenge. Light placement with respect to mounting height and light spacing should be a key consideration. If you run one xr30 you are going to struggle to get an even spread across 40 inches unless the light is fairly high up. It is a powerful light, but you are still likely to get a hotspot in the centre of the tank as the pucks on the XR30 G4 are close together. Further, you will also need to consider shadowing issues when the corals grow out. Another option is to have two xr15's spread about 14 -18 inches apart and raised up about 12 inches off the water surface. This should give you more even spread across the tank then the single xr30. However, to get the PAR you need you are probably going to have to run these close to max to get 250+ PAR at 12-18 inches of depth. A solution to this is to add a few T5's to supplement (check out the aquatic life hybrid). T5's provide a more subtle light source and will help with any shadowing you may suffer from with just two 90w LED lights. A further option is to have even more lights, if 3 xr15's isn't an option then a couple of AI primes for either side of the current xr15 may work well. Now completely out of left field.... have you checked out the Evergrow IT5012 / IT5080 lights. I think SAS have them (CB covid discount). ReefDorks youtube video on them is very compelling. These are growing in popularity and I have started to see more and more of these on various youtube/instagram show tanks. (Another light I know people are also keen on is the Illumagic Blaze X. Possibly the most common light over a three or four foot tank if you live in Australia. So many options!). Personally I would choose multiple xr15's not because they are better, but simply more adaptable. I know corals can grow under Radions so that isnt a problem. Couple the xr15's with the T5's and you will have a lighting rig capable of growing pretty much anything! Good news is you can build up your collection of lights slowly. Be good to hear what a few other have to say. Anyways Can't wait to see what you end up doing. Good luck! Sent from Singapore Reef Club mobile app