I am wanting to know how many fish could thrive in a 29 gallon (110 L) tank. Dimensions of the tank are 30” in L x 12” in W x 18” in H (76 x 30 x 46 cm). These guys could include any live bearers like guppies, platy fish and molly fish. In the future I am going to buy live plants so my tank is fully live-planted and not semi-planted. I currently have 9 fish which are 2 algae eaters, 2 platies and 5 guppies. I am just wondering so I don’t accidentally overcrowd my tank to where it is unhealthy or could cause problems to the fish.
The thumb rule is:
1 cm of fish for each 1 liter of water
- 1 fish, 5 cm/fish -> 5 liters of water
- 2 fishes, 2.5 cm/fish -> 5 liters of water
Now depending on which fish you want, and depending on their needs, you can make some estimation yourself.
As a kind reminder (it is sometimes forgotten): plants, filters, rocks do NOT count as water. With other words, take into consideration the water, and not the total volume of the aquarium.
Overcrowding can become a problem (the stress for the fish, the chemical balance of the water...). Under-crowding is unlikely to become a problem.
Also, do not forget that some fish prefer to live in schools (i.e. you need at least 4-5 of them, if you want them not stressed). Study the fish that you want to find out their particular needs.
I personally tend to overcrowd the aquariums, and I did not notice any problem. However, my behavior (and experience) should not be taken as science or as guarantee of success.