I live in a small house with  a wife and 2 teenage girls along with 15 years of 'stuff'. A fish room is out of the question. What I have is small spaces in the basement for my fish. I make use of the heavy metal storage racks that can be bought for $50-$75. They are 6 ft x 36" x 18" and have 5 shelves. Cut 2 x 4 's are added for strength for the shelves.

Top Row. 2 gallon tanks 2 A. scheeli, 1 Fp gardneri Akampa, 1 Fp. gardneri nsukka

Second row 2 gallon  1 no fish, 1 Fp. gardneri Biassa, 1 Fp. gardneri nsukka, plastic sweater box with grow out nsukka

29 gallon planted tank, lots of Cory bronze babies, 3 pairs of Blue Gularis, algae eaters.

3 10 gallon tanks, 1 Fp. gardneri Albino females, 1 Fp gardneri Albino males, 1 young Fp. gardneri Albinos

Top Row - 2 gallon tanks, 1 australes, 1 emtpy, 1 Fp gardneri nsukka, 1 Ap gabuense boehmi, 3 gallon tank with Fp. amieti

Second Row - grow out sweater box Fp. gardneri misage, 1 Fp gardneri Albino breeders, 1 Ap gabuense boehmi, 1 Fp gardneri misage, and on side is a tank of Ap bitaneatum breeders.

1 plastic file box gardneri Albino growout, 10 gallon with Cory's and australes, plastic file box with Blue Gularis breeders, and on back side a grow out box of Ap. bitaneatum.

10 gallon with australe males, 10 gallon with australe females, 10 gallon breeding group of Corydoras.

Tanks are lit with a 'bright stick' mounted on the underside of each shelf. I have another one of these racks, a couple of 29's on stands, and a wall bookshelf is starting to house rows of 2 gallon tanks also. This is the bookshelf where things are spreading out quickly.

Top Row 2 gallon tanks.

Fp spoorenbergi, Fp. gardneri mamfensis HAH 98, Fp. gardneri mamfensis Talangaye 95/6, Fp gardneri Albino

Fp gardneri Biassa, Fp. gardneri Jos Plateau, Fp gardneri Akure, more Albino's

Sympsonichthys constanciae males, females, newly hatched Fp gardneri nsukka

Big storage box for grow out of Blue Gularis

So this should show you that if you are tight for space, you can have a lot of different fish in a 36" x 18" space. And if you are like me, they are spread around because I can can't come up with a lot of space at any one place.