About HDPE Sumps
High-density polyethylene (HDPE) is a far superior material for aquarium use over glass and acrylic.
- HDPE tubs are one-piece molds instead of glued or welded, leaving no weak spots
- HDPE molded sumps have much stronger corner joints than glued or welded sumps
- Baffles and glass lid recesses are molded in, not glued or welded
- HDPE tubs have smooth, rounded corners, which are much easier to clean
- Nothing sticks to HDPE, including algae
- HDPE is highly resistant to chemicals and solvents
Molded vs Glued or Welded
The primary advantage of the Seamless Sump® is that the HDPE tubs are one-piece molds rather than multiple parts glued or welded together. These are the benefits:
The corners are the strongest parts of the tub.
Most acrylic sumps are machined/fabricated and have glued or welded joints. This means the corner seams are inherently the weakest part of the sump tub, as the adhesive and welding process creates a more rigid and brittle joint, making it weak and vulnerable to cracking over time. This issue is avoidable with a one-piece HDPE tub.
We use a rotational molding process to manufacture our Seamless Sump® tubs. A metal tool with the outer shape of the desired part is designed using a 3D computer model. Plastic resin is added to the tool’s core and heated up as the tool starts spinning in all directions. As the mold rotates, the HDPE slowly sticks and cools on the sides of the mold and takes the shape of the desired part.
As the tool is cooling, a thick layer of HDPE accumulates in the corners because it has a harder time flowing around the corners as it spins. This gives each corner joint a strength that most other sumps lack.
Baffles and glass lid recesses are molded in, not glued.
The Seamless Sump® Baffle Tub is the only aquarium sump where the baffles are molded into the part rather than glued or welded. This gives the tub strength, integrity, and also makes it easier to clean. Plus, many structural ribs and indentations are molded into the tubs, enhancing the strength of the tub’s flat areas.
HDPE tubs have smooth, rounded edges and corners
Another benefit of the rational mold process is that each tub corner has smooth edges with a large rounded radius. This ensures that the tubs are easy to clean and free of creases that harbor algae and bacteria.
Nothing Sticks to HDPE
No amount of algae, glue, epoxy, paint, or adhesive will stick to HDPE Seamless Sump Tubs®. On the other hand, acrylic is a porous material, absorbing chemicals, yellowing, and becoming brittle over time.
HDPE means no “Nasty Tub” Syndrome
HDPE is a semi-transparent, sort of a “milk jug” color, whereas acrylic is typically clear. The ability to see inside an acrylic sump might seem nice at first, but this is where all your debris and refuse end up, quickly turning your clear sump into a nasty, cloudy, yellow-green.
Meanwhile, our semi-transparent tubs are clear enough to see the water levels inside, but still hide the debris and discolored water.
If HDPE is so good, why are most sumps made of acrylic?
The main reason most aquarium sump systems are made of acrylic is because acrylic sumps are easier to fabricate. Anyone with a table saw and a can of glue or a welder can make an acrylic sump. However, the end result is not so desirable. They are typically prone to flaws, blemishes, and weaknesses. Because HDPE is molded, not glued, it requires a unique design with a significant investment in engineering and tooling. With our vast experience with servicing our own aquariums (SerenityUSA.com) we spent a lot of time and resources creating that unique design and went the extra mile with our tooling to create the highest quality, most comprehensive elegant filter system on the market.
Why is Glass the Best Choice for Aquariums but HDPE is the Best Choice for Sumps?
As we explain in our glass vs acrylic aquariums page, we strongly believe that glass is a better material for aquarium use than acrylic. However, when it comes to aquarium sump use we feel that HDPE is better than both acrylic and glass.
The main reason glass is used for aquariums is because it is clear, rigid, and scratch-resistant. There is no practical manufacturing process to make a one-piece molded clear aquarium in the variety of shapes and sizes that we offer. However, for aquarium sump use it does not matter what the clarity is of the tub so long as you can see your water line. In fact, having less clarity is an advantage as we explain above. Once you eliminate clarity from the necessary features, now weight, strength, and overall integrity of the material are the key factors. Because our HDPE tubs are one-piece molds that make them stronger than glued/welded acrylic, and they are much lighter and easier to manipulate, drill holes in, etc. than glass, it makes it the perfect choice for aquarium sump material.
