Yes that is in my 240gal tank. It is a purple digi.
Yeah it is pretty cool. Unless you flood the light to it, it turns brown. I believe it is fairly common. I break pieces off all the time and give them away. No one else can keep it that deep purple....at least around where I am at. Sometimes sold at German Blue Digi.
I have my Purple Digi directly under my 400 watt MH. Have had the same color with two different brand bulbs, both 20k. So I guess it is just the quantity of the light. Others have had it purple up, but not as bright, under over driven t5s. Again directly under the light. I can take a piece move it down, 12" and it will turn solid brown in a week or so. It really loves light.
I think if you put it right under the MH you might get the color, I put some in my 90 gallon tank right under my 150 MH and it colored up for me, but not as bright as the 240. Here is a bigger picture of it....
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