First off let me say I am not an expert on salt or freshwater but am good enough to keep and breed german rams and have been reefing for 6yrs with some trial and error but my current 49 tall reef tank is doing exceptionally well and I am growing SPS, LPS and soft corals with lightening speed! So I'm no newbie either.
Doing your research was your first step in the right direction but in that you should have seen that this tank is much to small for a pair of clowns they need atleast a 29 gal as at maturity the female of this particular type reaches 6 inches. Also 6 gallons will fowl very quickly and the first death or overfeeding can ruin the entire set up. Nano tanks are ment for the more advanced hobbiest and a bigger tank would have been easier to start with. Lastly you will not have room for many creatures in it as it is already past the fish stocking capacity for that size already. I am limited with my relatively small set up so you will be even more so.
I hate to be such a debbie downer and am not hating on your tank so let me tell you what I would do to fix it...First invest in a VERY good protein skimmer that is rated above the volume of your tank as you will need to over skim to keep it clean 10-15 gal would be ideal. Trade your clowns for a nice nano fish like a goby, basslet or fire fish. If you're interrested in the relationships of fish in the ocean you could even keep a prawn goby and it's companion pistol shrimp. You can keep the cleaner shrimp as you will desperately need his services and add 10 nassarius snails, 5 cerith snails, 5 nerite snails and maybe one small turbo snail as a good clean up crew, saltwater creatures direct on ebay will give you a great deal that's where I got mine. Order some copapods & amphipods as they are excellent detritivors and will help with the particles too small for snails and feed your corals and fish naturally, I also ordered mine on ebay 9.99 for 250 pods w/ free shipping and 9$ plus shipping for 500 tisbe pods..avoid hermits they are killers!
To make your tank seem bigger and maximize the number of corals you can keep stick with small soft corals like zoas and palys. These are beautiful, inexpensive and very forgiving of tank fluxuations. Also these and the kenya tree will act as filters to help keep nitrate levels stable. So Keep one kenya tree for height but I would trade the other. I very much doubt that a staghorn will live with the nitrate level that will build up quickly in that small of a system but if you want to try to keep the it mount it to a high corner of the tank it's self with apoxy in an area with turbulent water movement, preferably where the cleanist water will be directed onto it. If it lives it will grown out over the tank and will not shade out the softies as they can adjust to different light levels relativly easily. Just make sure it does not grow into the kenya tree as it will be stung, melt, and fowl out your tank.
On a more positive note you have excellent water flow and lighting....I love LEDs and my tank has never grown faster or looked more colorful than since I switched from metal halides. If you do get the zoas and palys this lighting will make the colors blow you away! You have a proper amount of sand that will act as a good buffer for nitrate spikes but you may want to add more liverock to help with that, also make sure it has plenty on coralline algae and no pest anemones.Please invest in a good test kit for your nitrate and phosphate to help keep them from building up, also for calcium, alkalinity and most important magnesium as it will keep the former stablized and help all your animals thrive. I really hope this helps and that I was not too brutal...I just want you to have the best reefing experience possible and for all your hard work and monitary investment not to end up in vain. To give you a better idea of what you should be going for I'm posting links to some awesome nanos on this thread.
Happy Reefing!!!
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/youtu.be/F8FLzVnR0rM
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/youtu.be/jId-kUGjwbs
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/youtu.be/m67dwV17F28
