Hi
I'm using in the big tank (200l) a main Comercial Led Unit 18W [LFL-C 18W] and a DIY extra GU10 to the background plants (that grow like crazy).
In this moment i'm using (in the DIY GU10):
3x GU10 4w | 4000ºk | 38º | 180 lumen | 526cd + 2x G10 6w | led smd | 4200ºK | 45º | 400 lumen | 830cd + 2x GU10 1,3W Blue led just for fun!
In my other tank (CovaMoura) i use only GU10. But is a nano tank with 20 liters...
3x 1.3W Blue + 2x 1.3 Red - for colour effect - 10/9 hours
2x 4W 6500ºK angle 30º - very powerfull, small light cone, no algae - 8 hours (very good optics, use this if you want light power in the substrate)
2x 3W 6500ºK angle 45º - correct power, no algae - 8 hours
4x 4W 4000ºK angle 45º - very nice color but some algae, also too much power - 4 hours
From my small experience with GU10 is very comfortable to use if you pick the right lamp!
Optics is crucial to send power to the deep of the tank. Lamps with only a simple difuser will give high power next to the lamp 10/20 cm, then we lose most of the energy... In a big tank the standard size of GU10 is comfortable to control. In a small tank can be tricky...
One advise that i followed is to keep away from high power and cheap lamps! Can burn easily since heat is badly dissipated!
I don't use any fan's and still haven't burned any lamp...
I try also to point each lamp to a specific group of plants... (at least i try)
I'm very curious about your solution and to learn a lot more.
Thank's for sharing your project
cheers,
tiago