Old topic but I just gotta know.... Question

Discussion in 'Freshwater Fish and Invertebrates' started by Reefdweller, Apr 1, 2012.

  1. ReefdwellerValued MemberMember

    Okay people - I know this is a question that has been asked many many times and I know it differs from person to person or 'expert" to "expert" BUT! What are your thoughts when it comes to how many fish is enough. I have read and heard it in all sorts of combinations such as 1 fish per gallon, 1 fish per gallon based on the max size of the fish when a adult, I have even heard that when figuring your gallons to add your sump gallon amount to the total (?).

    What it boils down to is regardless of what you hear, read and are told. What do you personally base your total on? Use your tank as how you gauge it. I have a 75 gallon and I have 25 in mine. They seem comfy and healthy so for me this works but I like to hear what others think when it comes to thier personal tanks.



  2. snapperWell Known MemberMember

    I go by water quality (how long it takes nitrates to get to my perceived upper threshold) and behavior (like so they seem to have enough space to be happy, are there territorial issues, etc.)

    In my 46 gallon I used to have a lot more fish, but they seemed crowded, so some of them got returned.

    Sent from my iPhone using Tapatalk

  3. Dlondon95Well Known MemberMember

    I never stock my tanks going by "number of fish".

    Things you need to take into account are size of fish (you wouldn't put 25 foot long fish in a 75g), bio-load (although the tank my be big enough for a fish, if they are large waste producers, the water quality will be terrible), and how much room the fish needs.

  4. Lexi03Well Known MemberMember

    I do something similer, also taking into account how many fish will be swimming in each level of the tank.

    My 75gal has 32 fish plus inverts in it, my 90 will have larger waste producers, so it wil only have 21, my30 gal currently has 19 plus inverts because the fish are smaller and are not huge waste producers.

    It is also important to include the girth of the fish when considering it's size.
  5. catsma_97504Fishlore LegendMember

    Number of fish is a meaningless factor IMO. Instead I base my stocking more on the needs of the fish, such as swim space, level occupied, adult size, filtration, ect. Also factor in waste production. Certain fish have a higher bioload.

    The inch of fish per gallon of tank water was designed to determine how many one inch fish to safely add to a tank. For example 10 neon tetras in a 10 gallon tank. The flaw with this "rule" is that you'd never want to keep a 10 inch oscar, pleco or goldfish in a 10G tank.
  6. ReefdwellerValued MemberMember


    I am sorry but what do you mean by the girth of the fish?
  7. Lexi03Well Known MemberMember

    How big around/wide/deep the fish's body is. I may have misspelled it, I'm good at that.

    I actually had to add up how many fish where in those tanks to make that post, I can tell you exactlly how many of each fish is in each of my tanks, but I had never bothered to total it before.
  8. Wendy LubianetskyWell Known MemberMember

    :;deteI was just reviewing this topic yesterday. There really is no magic equation to give you number of fish (like an inch a gallon). Several factors are important when defining overcrowding:

    Adult Size of Fish which includes body mass and lengh!!
    Waste Production: what they eat. Carnivorous produce more waste than herivourous and the total amount of food eaten (like Oscars eat alot of meat products and produce a lot of waste)

    Aggressive fish fill the tank up more quickly than non aggressive fish do
    Whether the fish will be spawning as adults

    You have to kind of take that all into account and come up with what is right for your tank in your situation. It is always better to error on the light side.

  9. bowcrazyWell Known MemberMember

    The “one inch per one gallon rule” is not a rule but a simply guild line and should only be considered when you are looking at fish like Guppies or Danios and should never be used with any of the larger fish. There are many more factors that need to be considered than the length of the fish and the size of the tank when looking at a stocking list.

    First thing you need to consider is the size of the tank, the shape of the tank, the type and quality of filtering system that is installed on it, how stable the cycle is, what the swimming requirements of the fish is and how much waste the adult fish will produce .

    The better the filtration system the better off your fish are because of the water quality is kept more stable. A poorly filtered 75 gallon will not be able to safely house the same number of fish as a properly filtered 20 gallon tank. Yes there is more water in the larger tank but over time it can still become toxic if not properly filtered. Testing the water quality is a must with any size tank but is more important the smaller the tank because it can become fouled quicker.

    The size of the fish at adulthood and the amount of waste it will produce is the next thing that has to be considered when stocking a tank. The number of fish is not nearly as important as the output of the fish is. 100 Guppies will not produce as much waste as 10 Goldfish will over the same 24 hour period.

    Testing the water quality on a regular basis is the only good way to know how a tank is doing and if it can handle the addition of more fish. A properly cycled, well established tank can handle the changes of adding more fish better than a newly set up tank can. This is because the bacteria colony has had time to become stable and less likely to crash the cycle. Now a small filter with the minimum amount of filter media is less likely to handle the addition of more fish than a larger filter stuffed with filter media would because the beneficial bacteria has more room to grow.

    You also need to look into what the swimming requirements are of the fish. Some fish are very active and require longer swimming areas than others do. Danios will spend most of there time darting from one end of the tank to the other in the upper 1/3 of the tank playing tag where as Angelfish spend most of there time in the center 1/3 of the water column and slowly move around but would produce more waste than the Danios. So as you can see the Angelfish wouldn’t need as large a swimming area as the Danios would and they would be happier in a tall tank where the Danios would prefer a long tank. If you had 5 Angelfish and 5 Danios the Angelfish would require a much larger tank than the Danios due to their size and waste production.

    A 75 gallon tank is a very nice sized tank which gives you lots of options in the stocking area along with decorating. The larger the tank normally means you can have more fish but you also need to consider how large the fish will be fully grown.

    You said you have 25 fish in the tank already but didn’t say what they are so it would be imposable to tell if your tank is slightly stocked, OK stocked or over stocked so I am not going to comment on that only how I tell if my tank is stocked correctly or not.

    The best advice I can give is post the number and type of fish you currently have in the tank and the number and type of fish you are looking to add so that you will get some feedback on what others think would work. I am sure you will get a few differences in opinion on what everything thinks if you just post “What do you think I should stock” so come up with a researched list and post it.

    I hope I have made some sense and haven’t seemed like I just rambled along. I am sure others will post their thoughts on your topic but this is what I consider when stocking my tanks. Good luck and happy fish-keeping to you!
  10. blu3dragon619Valued MemberMember

    imo i say 2gal per fish if they are going to grow big just to give them room to swim and be happy, would you be fine in a 1 gallon tank? lol
  11. ryanrModeratorModerator Member

    +1 bowcrazy - great answer :D

    Temperament of the fish should also be considered. Cichlids come to mind, whereby over-stocking is encouraged to curb aggression.

    For what it's worth - I have never subscribed to the "inch per gallon" rule (I mean guide). In my 16G, I have 1 x Endler, 5 x Neons and 5 x Glowlights, or approximately 11 inches of fish (I don't include my b/n catfish in the calculation). Whilst I could probably add more, when you look at the tank, it's easy to see that "it has enough". There's enough free space for the fish to swim, enough hiding places for them, and it's quite a happy little community ;)
  12. igrefigNew MemberMember

    in my experience i can honestly tell you that number 1 to every rule there is an exception and that number 2 just because a fish can grow to be 10 inches doesn't mean that it will. i catch a lot of grief for it but i believe it to be true and its worked for me

    i have an oscar who when i got him was maybe 3-3.5 inches in a little more then a years time hes grown to be maybe 4.5-5 inches

    to each his own but i will use the 1 inch per 2-3 gallon rule just as a guide
  13. Disc61Well Known MemberMember

    I agree to a point, many fish do not reach their full potential size for one reason or another. but the fish that is to reach 10 inches has a better chance of not reaching that size in a ten gallon than it does in say a 100 gallon. and if the fish only reaches 5-6 inches when its species reaches 10 might mean it was stunted by lack of room. which may also mean its inside organs may not be fully developed as well. but i agree with you in the end, the info is out there, we research it and look it over and over, but in the end it really is " to each his own"
    the 1 inch to 1 gallon ( so called rule) more a guide was created many years ago for the newbie to have a reference point, but as mentioned above, it was meant for the small species. but, normally the bigger the fish the bigger the bioload. there are way to many things to consider to just use the 1 in for 1 gl. i stock my tanks in numbers by deciding on a species, then researching them to see what they require.

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