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Barrel Tender V2
Barrel Tender V2
Barrel Tender V2

Barrel Tender V2

32 reviews
$ 209.99

The Barrel Tender is a unique device designed to automatically regulate reverse osmosis (RO) water production and greatly reduce the negative effects of TDS creep.  The Tender senses when the RO reservoir is nearly empty, then turns on the RO system until the reservoir is full.  This allows the RO unit to run for longer periods of time, which maximizes filter efficiency.  

New Features

New for the V2 Tender is a Neptune Apex and GHL Profilux aquarium controller integrated version, which allows you monitor and fine tune RO water production.  The aquarium controller version does require an Apex or Profilux controller and a break out box or input board, respectively.  We have several break out box options here. Also, the new housing design incorporates a super bright edge-lit acrylic top, so you can see when it is active even when tucked away in the corner of your basement.  Lastly, we upgraded several key components and made it even easier to install.  



Reverse Osmosis water reservoirs are conventionally difficult to keep full on a regular basis due to the need to manually turn the system on and then remembering to turn it off hours or even days later.  Larger remote vessels can run dry due to "out of sight, out of mind" circumstances, resulting in having no water when you need it.  We have even heard of people using timers, keeping their RO reservoir in a bathtub to prevent floods caused from forgetting to turn the system off, and other wacky solutions that lead to frustrations with aquarium keeping.  The Tender is a set it and forget it solution for top off water production.


TDS (Total Dissolved Solids) creep occurs when previously removed pollutants on one side of the RO membrane leach across into leftover water on the "clean" side.  When the RO unit is restarted, these pollutants are washed out with the first little bit of "good" water.  If you are using a Deionization (DI) postfilter, the DI resin then absorbs this little blast of pollutants, but the result is that the DI resin is exhausted faster.  Otherwise, the pollutants go into your aquarium.  You get this little pollutant blast every time the system switches on, even when using an autoflushing system.  Running an RO unit for just a few ounces of water at a time, e.g., each time your top-off pump turns on and opens a float valve, means you are effectively losing the benefit of the RO membrane.  Conversely, If your RO system is allowed to run for longer periods of time, that initial pollutant blast is largely diluted by the large volume of clean water that follows.  If you are using a DI postfilter, this means the DI resin only has to pull out the initial pollutants once for a large volume of water, rather than many times over each small on/off cycle.  The bottom line is you'll save a lot of money on DI resin replacement.


Footprint: 6" x 4.5" 
Height: 5"

Power: 12v 

Rated for booster pumps up to 135 PSI.  Requires an Auto Shut Off Valve (ASOV) on RODI unit.  The Apex version requires a Neptune Apex controller and a Break out Box

Using the Barrel Tender with a GHL Profilux requires a PLM-ADIN add-on board, and a db9 terminal adapter.  See this thread on for more details.

What's included:

Barrel Tender with your choice of control and plug type along with all the tubing, fittings and nuts and bolts to install on barrels up to 32" deep along with a drilling template. Extra rigid tubing for deeper water reservoirs is available here.

See this template for dimensions required for installation.  We include a cardboard version of this in the box for installation convenience.


Apex version installation and programming instructions

 Barrel Tender and Pressure Switch troubleshooting guide

Customer Reviews
4.9 Based on 32 Reviews
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Filter Reviews:
Hao V.
United States United States
Barrel tender v2

Very good!easy to install,hope it will work like the way it should and don’t flood my house. Very fash shipping Thanks

Richard M.
United States United States
Love it

Works great and looks cool, perfect finish product for a ato container or a big mixing station

Edwin C.
United States United States
Awesome product.

I plumb all my tanks with their ato

Billy .
United States United States
Takes the stress out of making your RODI

My wife used to make fun of how many times I would go downstairs to “double check” that I turned to valve off on my RODI unit after making water. I also used to use a float valve directly into the sump and Dan educated me on how my water was suffering from TDS creep with this approach. The barrel tender has made making my top off and water change water a hands off process that’s no longer a source of stress. I had a bit a troubleshooting with the high sensor which turned out to be human error but Dan and Justin helped Fix the problem with great customer support; I’ll recommend this unit to every friend with a reef tank to purchase upfront when they get an RODI unit to save them years of stress.

David M.
United States United States

I shamefully admit that I have flooded my floor more times than I would like to admit. This product has a sturdy well built cut off for when the sensor triggers. I just installed the system a few weeks ago and I have had zero bad things to say. I even like the light on top too, makes my RODI garbage can look a little more tech. The install and instructions were spot on. I also watched a few youtube videos that made it super simple. As long as you have a drill and some drill bits you can install this gadget. The value of peace of mind makes it worth the price IMO. It feels well built too. VERY WISE investment.