[littlefrog]

By no color do you mean pale, or green? I don't know any green flowered tillandsia (I don't know them all), except T. usenoides (spanish moss). Most are purple or blue. A nice red flowered one is T. albertiana.

I'd also suspect a nutrition issue, although if they are in a tank with frogs, it is hard to imagine what that could be. Usually more nutrition than most plants need in a frog tank.

 

[littlefrog]

Spanish moss is predominately yellow flowered, I believe

Looks green to me when it blooms in the greenhouse. Maybe yellow-green, I guess.

I must say I've never had much luck with the typical tillandsias in a viv. The ones you normally see, anyway, that are silver/grey colored. That color is an adaptation to high sunlight (think sunscreen). Don't think I can get that much in a tank. There are some species of tillandsia with very different foliage (look like vriesia or guzmania), like T. wagneriania. Those probably would do well.

 

[littlefrog]

Always variants on the 'typical' for any species, might well be a yellow one. Might want it, it is hard to find the flowers on spanish moss usually!

Another Tillandsia that might be worth trying in tanks is T. bicolor. I just got two from Ecuador this spring. Hopefully they will grow well. They look like small neoregelias, more than anything.