When I was gathering various tubs and containers to use in my aquarium maintenance, I wondered what plastic containers would be suitable and safe to use. I didn’t want a plastic container that would leach harmful chemicals into the water I was transferring.
The answer is simple and relates to those little recycle symbols on the bottom of plastic containers.
Decoding the Recycle Symbol for Aquarium Safe Plastics:
A plastic that is aquarium-safe will also be food-safe. This is to say, the best containers to safely store foods are the best to use for your aquarium maintenance needs.
The little recycle symbol (three arrows formed into a triangle with a number in the center) helps recycle centers to identify resin plastics of like kind. The best type of plastic for use with foods have the number 2 in the center. These are plastics made of high-density polyethylene (HDPE). Compared to other types of plastics that are categorized (numbers 1 through 7), HDPE is relatively stable and inert. This means that it doesn’t leach chemicals into food or fluids over time. This makes HDPE plastics with the #2 recycle symbol aquarium safe. From what I see, #2 plastics tend to be used for items with more strength and stiffness.
A close second to #2 plastics are #4 and #5 plastics. #4 plastics are Low-Density Polyethylene, or LDPE. #5 plastics are Polypropylene. Polypropylene plastics have a high tolerance to heat, so many microwavable containers are made of polypropylene.
The only food-grade plastic I would avoid for aquarium use are #1 plastics. These are PETE or PET plastics, often used for one-time items like plastic water bottles. These plastics are slightly more unstable and can readily leach chemicals if used over time.
I’d prefer seeing the #2 or #5 symbols for items I was using for an aquarium. My large Home Depot bucket is a #2 plastic. The remainder of the small Rubbermaid or Tupperware containers that I use with the aquarium are #5 Polypropylene.
Best Practices for Cleaning Aquarium Plastics:
I want to mention that beyond the type of plastic you use for aquarium maintenance, it’s important not to contaminate aquarium containers with soap.
I never use any soap on my aquarium buckets and maintenance Tupperware. Even new items purchased from the store, I only rinse with water to get them clean. If you use soap, you risk contaminating your tank – soap and your fish/inverts do not mix.
Even the best aquarium-safe plastics can be ruined if you wash them with soaps, so avoid that temptation – only rinse with water.