13. Stocking

If one is new to fishkeeping, stocking is best looked at not by numbers but rather by water clarity. Slowly add some fish. Then see how it goes. Keep looking down the length of the tank and judging how clear the water is. If the water looks even a little bit cloudy do not add any more fish till the cloudiness clears up. Don’t worry about numbers. Gage the stocking by the health of the tank. How clear is the water? When the water is clear, add more fish. Cloudy water? Wait a while, till the cloudiness or “dullness” clears. Then you can add more fish.  Simple!

Stocking and Opinions

The topic of stocking is largely OPINIONS, not experimentally derived scientific facts. Let me repeat that:

The Topic of Stocking is Largely OPINIONS

So do what YOU want to do with YOUR aquarium. If you want some guidelines which are largely just my opinions, read on.

The Science

Note that there is some science here. And the science says that VERY VERY HEAVY stocking of aquarium tropical fish is quite healthy and does little harm to tropical aquarium fish. The science is based on university research on the zebrafish and can be found in the following article:

13.2. Calculating Stocking Ratio (links to aquariumscience.org)

My Opinions and Recommendations

IN MY OPINION, the following stocking ratios, based on the volume of fish, are perfectly acceptable for a 100 gallon tank:

Number of fish for stocking in a 100 gallon or 378,54 liters aquarium

Total length of fish in centimetersLight stockingRecommended 100% level stockingHeavy stocking
2,593311933
52378233
7,61447140
1082678
12,751750
1531134
17,82720
201514
231412
25139
28027
30026
* ONLY with very heavy filtration

.

Labidochromis auratus Bearded Yellow Lab
Labidochromis auratus Bearded Yellow Lab

For a 75 gallon tank the stocking numbers are:

Number of fish for stocking in a 75 gallon or 283,91 liters aquarium

Total length of fish in centimetersLight stockingRecommended 100% level stockingHeavy stocking *
2,570231700
51758175
7,61035105
1061758
12,741338
152825
17,81515
201310
23127
25016
28015
30004
* ONLY with very heavy filtration
Peacock Fire Fish - Albino
Peacock Fire Fish – Albino

For a 50 gallon tank the stocking numbers are:

Number of fish for stocking in a 50 gallon or 189,27 liters aquarium

Total length of fish in centimetersLight stockingRecommended 100% level stockingHeavy stocking *
2,547155466
51239117
7,672370
1041339
12,72825
152617
17,81310
20127
23026
25014
28013
30003
* ONLY with very heavy filtration
Maylandi zebra OB
Maylandi zebra OB

For a 25 gallon the stocking numbers are:

Number of fish for stocking in a 25-gallon or 94,64 liters aquarium

Total length of fish in centimetersLight stockingRecommended 100% level stockingHeavy stocking *
2,52378230
561958
7,631236
102618
12,71412
15139
17,8026
20012
23011
* ONLY with very heavy filtration
Neocaridina davidi Blue Shrimp
Neocaridina davidi Blue Shrimp

For a ten gallon the numbers are:

Number of fish for stocking in a 10 gallon or 37,85 liters aquarium

Total length of fish in centimetersLight stockingRecommended 100% level stockingHeavy stocking *
2,51031189
53828
7,6259
10135
12,7023
15012
17,8001
* ONLY with very heavy filtration
Maylandia Red Zebra
Maylandia Red Zebra

For a five gallon the numbers are:

Number of fish for stocking in a 5 gallon or 18,93 liters liters aquarium

Total length of fish in centimetersLight stockingRecommended 100% level stockingHeavy stocking *
2,551590
51414
7,6024
10012
* ONLY with very heavy filtration

The heavy stocking columns for the ten and five gallon aquariums have been crossed out for a reason. The filters for small tanks are always very small cartridge or air operated sponge filters. These filters are just totally inadequate to support heavy stocking.  So small aquariums should not be heavily stocked. If one puts something like a very small canister filter on a ten gallon, one can think about heavy stocking. But I’ve never seen that done.

Nimbochromis venustus
Nimbochromis venustus

Now these numbers, especially the “heavy stocking” numbers, will absolutely send some “fish police” into absolute hysteria and get this site kicked off many Facebook forums. Remember, the heavy stocking levels are only “ MY OPINIONS” (not “rules”) based on WELL FILTERED AQUARIUMS WHICH HAVE LARGE FILTERS WITH GOOD MEDIA THAT HASN’T BEEN FREQUENTLY CLEANED!!!!!

In the in depth articles below I give my OPINIONS on the topic and the OPINIONS of others. It is all a rambling set of OPINIONS so unless you want to get really bored, stop right here.

Andinocara rivalatus Golden Saum
Andinocara rivalatus Golden Saum

Stocking in Greater Depth

Hopefully the following links can put some common sense into this subject:

13.1. Stocking Opinions (links to aquariumscience.org)

13.2. Calculating Stocking Ratio (links to aquariumscience.org)

13.3. Lifespan of the Fish (links to aquariumscience.org)

And the common or narrow bodied goldfish should be stocked as a five inch fish.

This is delved into in this link:

17.5. Goldfish (links to aquariumscience.org)

Cyrtocara moorii Blue Dolphin
Cyrtocara moorii Blue Dolphin

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Translated in dutch by : Joost Abrahams
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