A 55 gallon is going to be too cramped...it's only 12" deep, the minimum size of a healthy adult oscar. The fish would barely be able to move around. A 75 is the same length, but deeper.
Minimum tank size for an oscar?
- Thread starter reef95
- Start date
I think most seem to agree that a tank with a 48x18" footprint is the minimum for an adult. so, as mentioned 75 is a good size, but if you go that route, you might as well get the 90g version, its the same tank only 4 inches taller. looks much nicer and the added volume will allow a few tank mates plus extra water volume never hurt when dealing with big messy fish 
I think most seem to agree that a tank with a 48x18" footprint is the minimum for an adult. so, as mentioned 75 is a good size, but if you go that route, you might as well get the 90g version, its the same tank only 4 inches taller. looks much nicer and the added volume will allow a few tank mates plus extra water volume never hurt when dealing with big messy fish
I certainly agree with this as I have mine in a 90 with a 4.5 inch pink convict and a 13"common pleco. I run 2 Emperor 400's with 2 water changes a week. This barely keeps the tank clean. Plecos, like any other fish need to be fed as well. At that size they don't live on algae and are actually omnivores. Plus they like a bit of wood to rasp on so that adds to the waste (at least mine does).
In fact it is so silly to talk about the cubic volume of a living thing
In commercial fish farming - which is far more scientific based and far more efficient than Aquarium hobby- We use the weight of the fish to determine the water volume needed for every fish maybe that's a better way
It kinda depends on how long you're wanting to keep it, what your maintenance schedule is, and what you feed it. I bought a small female back in March, put her in a 55, fed her nice, expensive food, had triple the filtration, and did my normal WC's and she grew so much I felt it was best to give her to a new owner, with a much larger tank.
BettaFishMommy
finkids make me happy :-)
IMO, this calculation wouldn't work for ornamental fish that we keep in tanks at home. a long and slender fish could weigh the same as a shorter more stocky fish. the long fish needs a longer tank, i would think.
as for the efficiency aspect, your average fishkeeper would be more interested in the comfort of their fish as opposed to efficiency.
There is an actual mathematical formula that can be used to figure needs more accurately. I don't recall the formula but it takes length of a particular species and uses a formula to figure its median girth, weight, and approximate age. When it all is added up you come up with the minimum needs to sustain it. It also takes variables into consideration when you have 2 of the criteria. Sounds like a lot of work to me, just found it interesting.
mostlycichlids
Cichlid Specialist
I think there is a lot more to consider than water volume and size of the fish. 75g is sufficient for an adult Oscar but you can have tankmates in there as well with proper filtration and maintnance. I sucessfully keep a Female Dempsey, Convict and an Oscar in my 75g...the Oscar is not fully grown but fully mature. I do 50% water changes every 10 days as I do with all my tanks. I think the whole number of gallons and some minimums thrown around these days are sometimes rediculous. I just don't agree with only being able to keep just a lone Oscar in a 75g, I do agree a 55g is too small though. I also have learned that moderately stocking larger Cichlids IME cuts aggression and territory issues quite a bit.....just my 2 cents.
