Well first order of business is to either return that fixture or buy replacement bulbs. I mentioned the appropriate color temps earlier. Geissenann T5HO bulbs would get you the best results.
Now, from the link to that website with the moss being used in the tree. Beautifully scape and certainly something to strive for. However, there's more than just moss there.The ground carpet appears to be a combination of dwarf hair grass and Utricularia graminifolia.. These are examples of faster growing plants than the mosses. When you have a high amount of light without plants that can utilized it, you end up with algae. When you add plants that are considered medium to high light, they use that extra light you have and basically suck all the nutrients out of the water. If they're not there to out-compete algae, then opportunistic algae takes hold and grows rampant. Its all a balancing act with lights, ferts, co2 (or liquid carbon), and the right mix of plants...otherwise it will go south on you with excess light. Research will be your best friend.
Anyway, you can start off slow by reducing the light by running only two bulbs and with a reduced photoperiod (6 to 7 hours max). A two bulb T5HO would still be too much light for moss alone so consider adding more plants. Maybe some stems like rotala or ground cover like micro swords.
Liquid carbon such as flourish excel or API co2 booster can be used in lieu of injecting co2 -- although IMO, co2 injection is best. Money is tight, so for now you can even consider creating a DIY co2 generator (yeast/sugar) and supplement with excel. Not too much excel as it can hurt the moss.
What are you using for fertilizer?
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