This is what i plan on currently for a single figure 8, please give your comments
15gal high stock lights
2 aqua-clear mini, one with media, the other with the best buffer i can find (crushed coral or so)
pea gravel from home depot possibly with added crushed coral
an appropriate heater
i was thinking about trying to adapt some java fern or maybe even horn wort to brackish, might even try a moss ball. I'm not sure however on taller decorations.
I don't think a 15-tall is appropriate for an F8 personally. Nominal tank sizes are misleading, and the tall orientation isn't great. Why not do 3 DP's like you were originally thinking?
I agree with Lisa - the 29 would be better for a F8. I'd have no problem with a singleton. These fish live for so long that the cost of an additional tank is relatively minor - especially if you find a used one. For example, today, I found a decent 30 long at a yard sale for $10. And its holding water at the moment.
I have an additional concern about your filtration - IMO, the two minis are inadequate for that much deep water. I would look at a bigger AC.
I do think that F8s can be well entertained in a 15 high if there is plenty of current, over filtration, and plenty of rearranging of decor!
I know longs are normally better than highs, but if you are inventive I think a puff can be very happy in it. My F8 is going to inherit my 35 gallon eventually, but I don't think a 15 tall is a terrible option... meh, just my lowly opinion. These guys are way more experienced than me.
