| | Re: Failing for years =(
How large are those individual pebbles? They look like pea gravel, which is really difficult to grow anything in. Ordinary aquarium gravel would be better. Better still, get something that has some cation exchange capacity (CEC), like Flourite, Eco Complete, Turface, Safe-T-Sorb, or even plain kitty litter. Safe-T-Sorb is sold at Tractor Supply and is very inexpensive.
The jury is still out on LEDs, we just don't know which ones work and which ones don't. I think you will need at least 2 T5 HO tubes over your tank. If you get a 4 tube fixture, be sure it will work with less than all four tubes installed, or has two switches so that you can use just 2 tubes at a time. This gives you more flexibility on how much light you a putting on the tank.