Hm, it wouldn't just be the one tank for me lol!
My dream would be to firstly have an indoor pond room, with one 24-30ft long by 12ft wide and 3-4ft deep heated tropical indoor pond with a large Red Tailed Catfish in it, an oxydoras niger, some tiger shovelnose catfish and a small shoal of irredescent sharks or similar shark type catfish or some pacu etc.
It would be relatively sparsely decorated, just some giant branchs of driftwood, scattered boulders, slate slab rock waterfall, perhaps some water lillies too.
The second indoor pond would be about 12ft long by 6ft wide and 2-3ft deep, and would be full of large shoals of bala sharks and tinfoil barbs, large schools of clown loaches, some large plecos like common and sailfin plecos, maybe lotsa common livebearers, armoured shrimp, shoals of tiger barbs and torpedo barbs etc. Or i might change some of the smaller fish stocking to make it more oscar fish friendly, and have large numbers of oscars etc.
There would be a large slate slab rock waterfall at one end, the water would fall onto a mass of boulders and smooth rocks, towards the other end of the pond there would be water lillies and other thriving aquatic plants. As a substrate, there would be lots of fine white silica sand to contrast against the colours of the fish to its best.
Both ponds would be lined with white ceramic tiles, the room they would be in would be heated to humid tropical temperatures to keep the ponds warm, so i woudl probably also place large plant pots/containers with plants which love such conditions like tropical ferns and avocado tree's. Lighting would be provided by a glass section in the ceiling from above so natural sunlight could illuminate the ponds from above during the day, while underwater pond lights would light up the ponds during the evening and night etc.
Then as far as tanks go, i would get a 6x2x2ft tank and turn it into a raging river rapid sub-tropical tank set up, devoted to fish which thrive in the cooler tropical temps in fast water current conditions, like herds of hillstream loaches, yoyo loaches, weather/dojo loachs, danios like zebra and leopard danios, torpedo barbs, bloodfin tetras, white cloud mountain minnows etc etc. The tank would have strong lighting but little planting, it would have a fine sand and gravel mixed substrate and the tank would be full of smooth pebbles and boulders and scatted bits of driftwood with aquatic plants clinging to it etc...
Lol, i have a lot of dreams
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thinking of all these. 
i like the house in the tank thing. haha. i starting to think of many many tanks, something like a fish shop for that matter.
