Tropical Aquarium Expert

What Fish to Put in Freshwater 40 Gallon Hexagon Tank (Aquarium)?

I am fairly new to the aquarium thing but I have really enjoyed the small 10 gallon tank I had set up in my classroom. I took a gamble and found a great deal on a 40 gallon hexagon tank. It’s all set up and the water is stable and testing normal for everything. I’m ready for fish but I want to make sure i do it right. In my classroom I had a Dalmatian Molly that had about 25 babies, I didn’t do my research. I’d like to have a variety of bottom, middle and top swimmers since it’s a taller tank and I’d like a variety of color, size and interesting fish that will live peacefully. I’d like to stay away from live bearers since I don’t have the capacity to breed nor do i want a full tank of the same fish. Any suggestions or "fish lists" would be greatly appreciated! I’ve been researching and can find info on specific fish but I really want a list of fish that fit my needs and will live well together. Thanks!!
This hexagon is not very narrow, it’s actually quite stocky, 24" wide and 26" tall.

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3 Comments for “What Fish to Put in Freshwater 40 Gallon Hexagon Tank (Aquarium)?”

  1. Aquella

    This is likely not the answer you’re hoping for, but…
    Hexagon aquariums are built for people, not for fish. Their narrow and tall build leaves very little room for fish to swim, and lacks the surface area required to support anything but the lightest stock.
    Any active fish, such as Tetras, Barbs, Guppies etc. would be miserable in such a set up, and bottom dwellers have a hard time obtaining enough oxygen.
    I highly suggest that you return your hex for a rectangular version, which will give you many more stocking options.
    If that is not an option, a pair of Angelfish, (who are one of the few fish that actually tend to do well in hex. tanks,) along with a Gourami or other surface breathing fish would be all I’d suggest.
    Also, if you have not done so already, please read up on cycling your aquarium before you bring any fish home.
    Cycling info:
    Fish profiles:

  2. I win

    1 clown pleco (4" max)
    2 corydoras catfish (3.5" max)
    2 honey gourami (2" max)
    4 red-tailed rasbora (2.75" max)
    6 cherry barb (2" max)

    I don’t believe the below answer is accurate. Your filter is primarily responsible for introducing oxygen to the tank. Fish can live in a bubble if the filter introduces oxygen. Fish can die in a rectangular tank if there is no water flow. Regular tanks are better for viewing in my opinion, but you don’t have to return it if you don’t want to. Just buy a filter that is rated for a 40 gallon tank.

  3. Brandy

    Haha. Okay, I’ve read both the answers and they inspired me to weigh in with my opinion. :) Take it for what it is worth.

    Hexagon tanks are not my first choice in tanks. Generally they are very tall and narrow which is not ideal. They generally have a samller surface area than rectangular tanks, which means less oxygen exchange. Also, since they are generally taller, it is harder to properly filter the tank – the bottom of the tanks tends to just "stagnate" while the top half gets filtered. That said, you could put a submersible rotating powerhead at the bottom (Zoo Med makes an excellent one, btw) which would cancel out that issue. The other issue is that since they are generally taller rather than wide, this doesn’t give the fish quite as much "distance" to swim as a rectangular tank would. If you can return the tank for a more tradtional rectangular tank, that would be ideal. But hey – you might have the perfect space for this tank, you might’ve gotten a great deal at a garage sale, you fell in love with this shape of a tank, whatever – it is not a perfect world and you’ve got a 40 hex, and want help so here are my suggestions.

    Like I mentioned above, even though your tank isn’t a "standard" hex, I would still get a submersible rotating powerhead to help push that water up to be filtered.

    I would stick with tropical communtiy fish as these fish offer you the most variety (they stay small and are very colorful) and are most economical.

    Personally, I would do (an incomplete list)
    hatchet fish
    rummynose tetra
    female sunset coral dwarf platys
    glo-lite tetras
    ghost shrimp

    As for fish, here is a site you might find useful – just be sure you cross check the fish as to their "family" (community, semi-aggressive, etc.) as this list has them all thrown together.

    Hope this helps and best of luck!

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