I have 8 neon tetra, a beta and 8 mystery snails. My tank is a 15 gallon moderately planted (6 java long fern, 4inch square of christmas moss, a bit of java moss, 6 small short hairglass, 2 small anubias and a Cabomba caroliniana). The tank is filtered and heated. I also have some air buble in there too to help with air in the water.

So following the 1 gallon per inch of fish I get to about 12gallon used (neon about 7gal and beta 5gal)

I read at several places that gor mystery snail the rule is 1 snail per 2.5 gallon.

Do I add the fish to the snail to count the total of used space or not?

1 Answer 1


The stocking rule is very often subjective to other factors beyond just the size and quantity of the fish in the tank. Water changes, type of fish, tank mates, keeper experience, potential adult size are just some of the factors that should be used in determining reasonable stocking.

I've been keeping fish for about 25 years now, and I consider a tank overstocked when the crowding creates aggression or an unhealthy social environment, fish are being stunted due to inadequate water quality (basically the fish grow to the size of the tank myth), the fish are physically or ethically too large for the tank, or the biological filtration of the tank can't keep up with the nutrient supply created by feeding and waste. In your case, I suspect none of these conditions are anywhere close to existing, assuming you have a reasonably sufficient maintenance routine.

The 1" per gallon rule is a really broad, and IMO a really bad guideline. In your case, tetras are extremely small bodied fish, so if you are using that guideline, you can safely exceed it by quite a bit. Conversely, if you are stocking a large bodied fish, fish with very high metabolism, or a fish that are very messy, the rule can easily come up short.

Also, do not count snails and other inverts into the stocking equation unless they are sizable enough to be a major nutrient contributor to the tank. Snails and small shrimp should be excluded. If you had something like crayfish or other larger inverts, I would factor them in, but something more like a fraction of the 1" per gallon rule.

  • In my case I had 2 really large snail (with bigger shell than 1.5 inch) so those might have contributed. I finally removed the snaill this morning because they were making a rampage on my plants... I might add one or two latter when the tank is more planted. Thank you for this great answer who basically cover all my points
    – Rémi
    Commented Sep 11, 2015 at 20:05
  • @Rémi Are you sure? Many water snails aren't capable of eating any healthy plant. Maybe the water just isn't right for the plants. Did you check that?
    – Mario
    Commented Sep 13, 2015 at 5:15
  • @Mario My water hasn't changed after i added the snail. The plants were right before and do fine since I removed the snail. They ate complete leaf of my anubias and broke free many other parts from other plants i have in there
    – Rémi
    Commented Sep 13, 2015 at 5:19
  • @Rémi Which kind of snails? Tylomelania? Some of them just love digging, possibly pushing themselves under or through plants, but they restrict themselves to algae. Maybe your aquarium is simply too 'clean'?
    – Mario
    Commented Sep 13, 2015 at 5:23
  • @Mario They were mystery snails. I don't know mutch more but yeah I think my tank was too clean to host that mutch snails
    – Rémi
    Commented Sep 13, 2015 at 5:25

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