How many different types?

[Doggiedog]

I plan on switching over my 180 gallon to a loach/barb tank and was wondering how many different types of loaches could I keep in this sized tank?

[Diana]

Depends on the size of the fish.
a) Pretty much keep similar sized fish. Fish that are a lot smaller may get eaten by the larger fish.
b) Loaches and most Barbs are social fish, and I would suggest planning to keep them in groups of at least 5.
c) Big fish produce significantly more waste than small fish.
d) When you are looking up each species make sure they are compatible for water chemistry, including temperature, and water movement.

Here are a few stocking ideas:
Foot long fish:
5-8 Clown Loaches, or similar sized Loaches
5-8 Large schooling fish that get about the same size, (Bala Sharks, Tinfoil Barbs... Caution: many Barbs are plant nibblers!)
5 Senegal Bichers or fewer, larger ones. (Ornates are nice looking) (These are predatory fish)
A pair of Bristlenose Plecos (4-6" fish, but they won't get eaten) or a showier, large Plec like a Sail Fin, an Adonis or other.

Half-foot long fish:
5-8 Yoyo Loaches
5-8 Kubotai Loaches
5-8 Clown Barbs
5-8 Parkinsoni Rainbow Fish
A pair of Bristlenose Plecos

4" Fish
10 Zebra Loaches
20 Kuhlie Loaches
10 Corydoras Trilineatus (actually most Cories get to about 2")
10 Congo Tetras
10 Beosemani Rainbows
4 Clown Plecos, Candy Stripes, or a pair of (you guessed it! BN)

Specialty set up- River tank with all sorts of mixed Hillstream Loaches. Many of these fish are around 2-3", and there is tons of room for them. Caution: Some species tend to be more territorial than others.
20 Small Danios such as Zebras, but I would get a fancier species.
20 White Cloud Minnows.