I've got a little 18x12x12 inch tank which is lit by an arcadia 2 x T8 14 watt (15 inch) tubes luminaire. I'm able to grow everything i want under them (Glossostigma, eleocharis, crypts, anubius, java fern etc.). However, I have got to move the tank. As the tank is really old it's looking a bit scruffy (few scratches, and old algae under the silicon), so I'm planning on replacing the tank (and the substrate) and keeping all the other equipment. If I want to continue to use my existing luminaire I'm constrained to an 18" tank, but in the spot it's moving to, there's room for an 18x15x15" tank. that would give me 50% more volume, and three (count 'em!) inches extra of depth and height - may not sound a lot, but it's a big deal on such a small tank as this. Anyone got any views on whether increasing the tank size will leave me seriously underpowered in the light department? I don't want or need the highest lighting possible, just to be able to continue to grow the plants I already can - I think the highest light using ones are the glosso and the hairgrass. Thanks for any thoughts or advice.