What is an Overflow Box and Why You May Need One

What is an Overflow Box and Why You May Need One

What is an Aquarium Overflow Box?

An aquarium overflow box is a column or box used to control water flow. Overflow boxes -also known as "pre-filters", "skimmers" and "weirs" are usually attached to the inside back corners of an aquarium. They can also be attached to the back wall, in the center of the tank for unobstructed viewing from all sides, or on one end in peninsula tanks. All overflows have slotted tops so the water can pass but livestock stays behind. They are almost always used in conjunction with an external filter.

Why do I need an Overflow Box?

One of the most important considerations for a healthy aquarium environment is the tank's water surface area. Much of the dissolved oxygen in the water comes from where the air is in contact with the water. The surface is also where much of the undesirable elements build up such as proteins, bio-waste and uneaten food. When these elements build up on the surface, less oxygen will be able to enter the water. Excess waste on the surface also decomposes faster into the tank rather than being filtered out. Overflow boxes are designed to channel water from the surface into the box and onward to the filter, hence the name "skimmer box".

Overflow Boxes are safer.

Another important benefit of properly designed skimmer boxes is that they prevent total aquarium drainage in case of a power or equipment failure. The water level is allowed to drop only to the bottom of the slots and no further.

Overflow boxes can augment your existing filtration system.

A great way to boost your aquarium's filtration capacity is by adding bio media into the overflow box. Be sure you use an open style media so that water flow is not blocked. Overflow boxes are also great places to add carbon or other water conditioners when they are placed in open mesh bags.

You can go even further by placing an open cell filter sponge on top of the media, right below the intake slots or even behind them. The key here is the sponge needs to be "open cell" otherwise it will not allow the water to flow through. Using a sponge here makes it easier for the external filter do its job.

What types of Overflow Boxes are there?

Most overflows are literally boxes or columns. Box style overflows need to have an attached, leak proof bottom as well as sides. They are typically attached to the rear or side walls of the aquarium. With box style "Bird's Nest" overflows, there needs to be a plumbing hole(s) drilled through the wall of the aquarium or you will need to use siphon tubes going over the top edge. They are an easy and inexpensive option for retrofits and smaller aquariums but they are not our first "go to" choice. Siphon tubes are not reliable and we do not recommend this type of setup.

Column style overflows extend from the surface all the way down to the bottom of the aquarium. Column style overflows can be rectangular, square or trapezoid. These are the preferred type of overflows and are more versatile.

Another big advantage of column style overflow boxes is they can conceal return lines from the filter. Water lines returning to the aquarium from the external filter, which is usually in the cabinet below the tank, can be routed back up through the overflow box. We call these internal returns and over forty years ago, were the first company to offer them.

The Tenecor® advantage.

Overflow boxes are often one of those overlooked items. However, they are critical components in a well designed aquatic system. A poorly fabricated overflow made with off gauge inferior acrylic will fail. Maybe not tomorrow or next week, but it will fail. Seams may develop leaks or seals will rupture due to poor edge finishes. Inferior, off gauge acrylic will also warp over time.

Tenecor® overflows are fabricated from top quality cell cast acrylic. They have thicker walls and better seams. All edges are polished smooth for easier installation. You won't find any rough unfinished saw cut edges in any Tenecor® product including our overflow boxes.

Tenecor® overflows  are offered in over 2,000 standard styles.

We have the widest variety of sizes, colors and styles. Closed bottoms or open. Square corner boxes, center tanks, middle towers. Black or blue. All standard.

Tenecor® overflows ship free.

We don't charge for standard shipping for USA orders. Expedited shipping is available for additional charge.

The Tenecor® EZ Swap Lifetime Guarantee.

Our EZ Swap Lifetime Guarantee is designed to for your peace of mind and the health of your aquarium. We don't expect our customers to rip out a possibly defective overflow box, send it back to us and then wait for a replacement all the while their aquarium goes without filtration. Our EZ Swap Lifetime Guarantee means we send out the replacement before we expect you to return the defective one. Learn more here.

Finally, we offer a 30 day money guarantee on any overflow or internal filtration product.