DIY tank divider/separator


PVC, light diffuser divider installed on a 20g long tank. Photo by author.

If you’ve ever had to isolate fish, for any reason, you know there are several ways to do so. The best method to use depends on why you need to isolate the fish. Below are a few options:

  • You can move a fish to its own tank.
  • You can put a fish in a breeder box (either a hang-on or submerged). Or you can make your own custom isolation box, like the one I posted about here.
  • You can put a divider in the tank where the fish already resides.
  • You can put a divider in a hospital tank to treat multiple fish simultaneously while keeping them separated.

The last two options above are the focus of this post. There are commercial-off-the-shelf dividers you can purchase from your LFS, box store, or online. On the other hand, you can also make one yourself at a very low cost. It only requires three things – light diffuser (I like Plaskolite), PVC pipe, and small suction cups.

The sizes of the components above will depend on two variables 1) the size of the tank the divider is going into and 2) the size of the fish you’re separating/segregating. Larger size fish will require a mechanism to hold the divider more securely in place.

I like to use light diffuser. It can can be picked up at nearly any hardware store or big box stores like Lowes and Home Depot. The one drawback is that diffusers typically come in large sheets (22″ x 46″). Thus, you’ll most likely have to cut it to size. See photo A. There are other items you could use as the divider itself, such as sheet sponge that you can pick up at your LFS. The sponge below (photo B) is 20″ x 12″ and about 3/4″ thick. Using a sponge has the benefit of adding some biological filtration to your tank, but it also will need to be removed and cleaned periodically, depending upon how long you segregate the fish. Also, remember if use a sponge and you remove it to clean it, you’ve also removed the divider. This is one reason I prefer light diffuser.

(A) Plaskolite sheet cut. Photo by author.
(B) Sheet sponge. Photo by author.

Like sponge or light diffuser, PVC pipe also typically needs to be cut to fit. Though you can get shorter pieces sometimes, it’s most commonly sold in 8 foot lengths. I use 3/4″ 200 PSI (thinwall) because it’s easier to cut the channel into. The 480 PSI is thicker.

The suction cups can be bought at your LFS or online. You may also have some leftover suction cups from a canister filter, if you’re not using them to secure the intakes/outtake hoses on the tank. Standard submersible heaters typically also come with suctions cups that you can use if you don’t use them to secure the heater. If the fish you’re separating are larger species, suction cups may not hold. There is always the option to silicon the PVC to the glass, but that’s a more permanent solution.

To make the PVC supports, cut two pieces at about 5-6″ each. They don’t need to be very long (shorter will also work, especially for shallower tanks). Take each of your short pieces and cut a channel lengthwise. I use a Dremel to cut mine, but you can use a hack saw or other tool. By creating a channel, you’re creating a “groove” to slide the light diffuser into (see photo at top of this post). Drill two small holes in each of the PVC pieces. This is where you insert the attachment ends of the suction cups, with the cup side outside the PVC. See the photos below:


PVC tube for divider, suction side down. Photo by author
PVC tube for divider, suction side down. Photo by author
PVC tube for divider, suction side up. Photo by author




Leave a Comment