new ideas for sw tank

I have a 24x12x17 inch (60x30x43cm) sw tank. t the back it has a 24x17x4inch filter area and underneth a 24gal sump. I have two 1200l/h(320gal/h) powerheads. one circulates the tank and the other is the return from the sump to the tank, giving pretty good circulation. I have a protein skimmer running on a 2000l/h (534gal/h) powerhead. I also have tons of plastic bio balls about 1 inch in diameter and kilograms of ceramic bio balls in the sump along with a 300W ceramic heater with external thermostat.

I have a 2-3inch sand bed(taken from one of the islands in Taiwan) and about 20lbs of live rock. this all under a 36W plo light with one daylight bulb and one actinic bulb on for about 12-14 hours a day.

I had a picasso triggerfish which i was growing a bit while i waited for a larger tank but he has passed away as im new to saltwater tanks and he was not a good specimen to buy. The tank had cycled for 3.5 weeks. he was with a 9 inch snowflake eel who now lives alone and happy as larry.

now that u have the info i can ask the questions.........I want to go semi reef with inverts like feather dusters and such as i have a few already (unidentified) that came witht he live rocks. I cant go reef as i cant afford a chiller and the weather here is stinking hot. Also the snowflake limits me with mobile inverts like shrimp and crabs which i dont mind. what else could i put with the eel( who will a few months down the line go to a bigger home that i find for him. I would like a selection to look at at not just one fish that can live with the eel.

also i want to tank the third section in my sump and turn it into a small refugium. can i do this with a 13W globe that will be lighting about 7-8galsof water and if so what inverts and other life can i put on thye refugium to make it most produtive.

i will be adding another light identical to the one i have in the next month or two. or should i go for the daylight red bulb combo option??

sorry its a lot to read but the more info i give u the better advice u can give me.

thanks

yea i wnt the fish more than the reef at the mo. so i was thinking maybe a feather duster or two and the some fish other than damsels as i have 2 in a smaller tank. so can it be done?