1 (844) 338-5520 Call 125 W.Victoria Street, Gardena, CA 90248 Location

APEX AQ-4041 Aquarium RO/DI Water Filter System - 4 Stage - Made in USA

Click Thumbnail to Zoom

APEX AQ-4041 Aquarium RO/DI Water Filter System - 4 Stage - Made in USA

Availability: In stock


Scroll to Options


Clean Refreshing Aquarium Water for Your Fish & Plants

When you choose an APEX water filter, you'll get the absolute best water filter system for your needs from a company that values your business and will go above and beyond to ensure your full satisfaction.

Built in U.S.A.

Not only can you feel good knowing that APEX Water Filters gives Americans good-paying jobs, but you can also be certain that we carefully monitor each step in the manufacturing process because we produce our filtration systems locally.

If for any reason you're not completely satisfied with an APEX Water Filter, we'll replace it or refund the purchase price--no questions asked.

Quality Guaranteed

APEX Water Filters guarantees that our systems will meet your water filtration needs.


The AQ-4041 is built around our AQ-4040 but adds extra water-quality monitoring features. The AQ-4041 has four stages of filtration. The 5-micron filter cartridge protects the reverse osmosis membrane and improves water quality by removing sediment, insoluble iron and other solids that can foul the RO membrane. The 5-micron activated carbon block adds a second layer of protection by removing chlorine, chloramine and organic chemicals. The thin film composite (TFC) reverse osmosis membrane removes algae promoting phosphates and silicates along with harmful nitrates. After passing through the RO filtration unit the water flows through a mixed-bed deionization cartridge. This special blend of ion-exchange resins scavenges any traces of nitrate, ammonia, phosphate, silicate and heavy metals like copper and lead. The pressure gauge indicates when the system is clogged and requires new cartridges. We also added a digital Total Dissolved Solids (TDS) meter that monitors the water quality flowing out of the filter system. TDS is a general measure of all the dissolved substances in water. When the meter shows an increase in TDS, it is time to service the filtration system. If your tap water has nitrates, phosphates and silicates you’ll see an immediate improvement in your aquarium once you switch to RO water! If you’re growing live plants it will be easy to keep the water soft and pH low with RO water. This filtration system will remove water hardness and alkalinity, making it easier to create the soft acidic water aquatic plants and acid-loving fish need to thrive. Replacement 5-micron sediment filters, 5-micron activated carbon pre-filters and TFC reverse osmosis membranes and deionization resin cartridges are available.


  • Four-stage reverse osmosis filtration system
  • Granular activated carbon pre-filter for chlorine removal
  • TFC RO membrane removes up to 98% nitrate and phosphate
  • Mixed-bed deionization post filter cartridge for super-high quality water
  • Digital TDS meter to monitor water quality
  • Makes up to 100 gallons of water per day
  • Assembled with high-quality John Guest fittings for easy cartridge replacement
  • Made and wet-tested in our US facility
  • Pressure gauge to monitor filter system efficiency
  • Made and wet-tested in our US facility
  • Includes 3/4” non-corrosive garden hose connector for easy installation-nothing else to buy!

Warranty * Household water pressure can cause leaks and damage the surrounding building or fixtures if not properly installed. User must check all fittings for tightness. APEX assumes no responsibility for water damage due to leaks.

Options & Upgrades