How many neons would one choose for a tank measuring 36"X12"X18"? I want at least 10 but have researched that I could house upwards of 20 with my stocking plans. Any insight of how many one would get? I have plenty of filtration, around 110gals worth. They would be the only school kept and I like schools that actually stay in a school plus I like lots of colour which is why I choose neons. Besides scavengers the only other residents would be a pair of dwarf gouramis.

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30 Gal breeder: 2 Honey Gouramis, 3 Sterbai Corries, 8 Black-Skirt Tetras, 1 Albino Bristlenose Pleco, 1 Common Pleco (temporary home) and 2 Nerite Snails
10 Gal SW nano: 10 Pounds Live Rock, 2 Red Trochus

Neons don't swim in a tight school but each one swims in a different circular pattern. They also like to spend a lot of time in middle part of their tank. You seldom see them feeding at the top or bottom of their tanks. Some of my larger neons will swim by themselves at the different ends of their 55G tank, usually near the bottom.

Neons are not schooling fish, they are shoaling fish.

You can easily do 20 neon or cardinal tetras in that size tank with the gourami's. What "scavenger" fish do you plan on putting in there?

Whoops, I ment shoaling. Currently there's 5 Black Skirt tetras in there that are about 2 years old and there were 6 columbian tetras plus a firemouth but a recent heater malfuction killed the majority of my fish so now I stand at 5 black skirts, 1 columbian, 2 sterbai corries, a bristlenose and 2 nerites. My LFS told me they'll do an exchange with my Black skirts and single columbian so I figured I would go with neons as I prefer plenty of movement plus the colours of the neon adds coulour too the tank. I'm planning on restocking my tank so I was thinking about trading the 2 sterbais for kuhlies as I like the asthetics of the loach along with that the fact that sterbais are nearly impossible to find around here. The sterbais I had came from a breeder 8 hours away that I happened to find when I was there a year ago. So my scavengers would include corries or kuhlies, a bristlenose, and 2 nerites.

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30 Gal breeder: 2 Honey Gouramis, 3 Sterbai Corries, 8 Black-Skirt Tetras, 1 Albino Bristlenose Pleco, 1 Common Pleco (temporary home) and 2 Nerite Snails
10 Gal SW nano: 10 Pounds Live Rock, 2 Red Trochus

The general rule for stocking is 1" of fish per 12 square inches of surface area. By your tank measurements it seems you have a 30 gal breeder. You could put 45"-50" of fish in your tank. Note that these numbers are maximums. This is just a rough number and depends on the specific fish, filtering, amount of gravel-rocks-plants etc. They all reduce water volume. Make sure you are counting the fish at their full grown size.

Jumpins that would be quite a few! I just got back from my LFS and I currently have 3 black skirts and 2 honey gouramis drip acclimating so that will bring my stocking to 8 black skirts, 2 honey gouramis, a bristlenose, 2 nerites, and 2 sterbai corries. My next addition will be 4 more sterbais so that would be the tank mates for the neons. I'm currently working on lowering my ph to a better range for my fish, it was a little over 8 now it's down to 7.5 or so after 3 days using peat pellets so after I'm done tinkering with it and adding the corries in a few weeks I'll go about figuring out how many neons to add, if any. Would it be safe to add neons with my final stocking?

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30 Gal breeder: 2 Honey Gouramis, 3 Sterbai Corries, 8 Black-Skirt Tetras, 1 Albino Bristlenose Pleco, 1 Common Pleco (temporary home) and 2 Nerite Snails
10 Gal SW nano: 10 Pounds Live Rock, 2 Red Trochus