Where did you get 6gph for Aquaripure nitrate filters? There's no stated flowrate on the website that I'm aware of but I've calculated the flowrate before based on the largest filter's 90 gallon equivalent weekly water change and it's a lot slower than 6gph. 90gpW ÷ 7days ÷ 24hours = 0.54 gph. I came up with another way to calculate the gph to verify it.
Aquaripure denitrators' flowrates/gph are basically like automatic drip systems which use very slow driprates and calculating weekly water changes can be difficult when driprates are used. Luckily, there's a handy calculator to help us with that:
http://www.angelfish.net/DripSystemcalc.php
Also, calculating gph based on the water change volume will vary depending on the tank size (total volume changed), so I'll use both the minimum and maximum recommended size tanks to calculate gph for each denitrator: small, medium and large. That way, I'll be sure to get a full range of gph values
Using the Small Aquaripure denitrator ... "the Small Aquaripure [is] the equivalent of up to a 20 gallon weekly water change." It is recommended for aquariums between 20 - 50 gallons. What driprate does it take to perform the equivalent of a 20 gallon weekly water change on a 20 and 50 gallon tank?
On a 20 gallon tank, a 20 gallon weekly water change (100% total water volume) takes
1.18 gpH, 28.3 gpD, 198 gpW.
On a 50 gallon tank, a 20 gallon weekly water change (40% total water volume) takes
0.15 gpH, 3.65 gpD, 25.6 gpW.
Using the Medium Aquaripure denitrator ... "the Medium Aquaripure [is] the equivalent of up to a 50 gallon weekly water change." It is recommended for aquariums between 55 - 115 gallons. What driprate does it take to perform the equivalent of a 50 gallon weekly water change on a 55 and 115 gallon tank?
On a 55 gallon tank, a 50 gallon weekly water change (90.9% total water volume) takes
0.78 gpH, 18.83 gpD, 131.81 gpW.
On a 115 gallon tank, a 50 gallon weekly water change (43.48% total water volume) takes
0.39 gpH, 9.373 gpD, 65.6 gpW.
Using the Large Aquaripure denitrator ... "the Large Aquaripure [is] the equivalent of up to a 90 gallon weekly water change." It is recommended for aquariums between 110 - 300+ gallons. What driprate does it take to perform the equivalent of a 90 gallon weekly water change on a 110, 300, 400, 500, and 750 gallon tanks?
On a 110 gallon tank, a 90 gallon weekly water change (81.81% total water volume) takes
1.11 gpH, 26.78 gpD, 187.46 gpW.
On a 300 gallon tank, a 90 gallon weekly water change (30% total water volume) takes
0.64 gpH, 15.3 gpD, 107 gpW.
On a 400 gallon tank, a 90 gallon weekly water change (22% total water volume) takes
0.59 gpH, 14.2 gpD, 99.4 gpW.
On a 500 gallon tank, a 90 gallon weekly water change (18% total water volume) takes
0.59 gpH, 14.18 gpD, 99.26 gpW.
On a 750 gallon tank, a 90 gallon weekly water change (12% total water volume) takes
0.57 gpH, 13.7 gpD, 95.9 gpW.
The 300 GL tanks and above are very close in their gph suggesting this is the range where the large Aquaripure driprate operates.
According to this method, Aquaripure denitrators have varying flowrates as low as 0.15 to as high as 1.15 gpH but this is only because of smaller tank sizes and
equivalent water change volume. The flowrate (gph) through the denitrator remains constant. The Aquaripure Large Denitrator or Nitrate Filter typically operates around 0.57 to 0.64 gpH which is its actual gpH.
It turns out that my other method of calculating the flowrate based on the largest filter's equivalent weekly water change of 90 gallons works out very close. 90gpW ÷ 7days ÷ 24hours =
0.54 gph. That's much more simple.
http://aquaripure.com/shop/aquaripure-nitrate-removal-filter/large-aquaripure/
Are you planning on carbon dosing? I hope to finish my denitrator this weekend too. It'll be in a tank without fish so I can add and measure nitrate with potassium and calcium nitrate and phosphate with potassium and sodium phosphate and other chemicals needed to build up the water (it's too soft).
I'll dose carbon per the Aquaripure instructions: 4 ml every 3-4 days with the same amount of bacteria supplement until the denitrator is fully cycled. Then I believe it calls for dosing 4 ml carbon every 2-3 weeks in its port but I'll dose less more often.