Figuring my Ferts

March 22nd, 2008

Recently, after not quite being able to figure out what was going on with the fertilizers and algae in my 40G, I went on a meticulous 2-week testing schedule, where everyday I tested the levels of the two macro nutrients I suspected were out-of-balance, nitrate and phosphate.

DATE N (ppm) P (ppm) Changes:N P K
Day 1 5 .5 0 (WC) 0 (WC) 0 (WC)
Day 2 7.5 .5 15mL 10mL
Day 3 7.5 .5 10mL 15mL 10mL
Day 4 5 1 25mL 5mL 10mL
Day 5 7.5 1
Day 6 2.5 .25 30mL 20mL 20mL
Day 7 10 1
Day 8 5 .5 10mL 15mL 10mL
Day 9 7.5 .5 10mL 20mL
Day 10 7.5 .25 20mL 10mL
Day 11 7.5 1.0
Day 12 0 .5 30mL 15mL 20mL
Day 13 7.5 1.0
Day 14 2.5 .25 30mL 15mL 20mL
DATE What to add
Day 1 4mL Flourish
20mL Excel
4mL Iron
2.5mL N
2.5mL P
Day 2 10mL Trace
4mL Excel
4mL Iron
Day 3 7mL K
4mL Excel
4mL Iron
Day 4 10mL Trace
4mL Excel
4mL Iron
2.5mL N
2.5mL P
Day 5 7mL K
4mL Excel
4mL Iron
Day 6 3mL Flourish
4mL Excel
4mL Iron
Day 7 Water change

I dose my 40G aquarium using Seachem’s full product line of aquarium fertilizers, minimizing my costs by only buying 2L bottles of fertilizer solution, which usually last me some time. Up to this point, I had been following Seachem’s recommended dosing chart, which for a 40G aquarium calls for the dosing schedule on left.

What I essentially confirmed, when comparing the two charts, is that I was vastly under dosing my aquarium, particularly the macro-nutrients. Over the course of my experiment, as I adjusted my dosing levels according to the test results, hair algae disappeared from the tank. The plants really took off, and were looking much more healthy than before, especially plants such as Blyxa japonica that feed mostly from the water column. Although I didn’t document my trace and iron dosing levels, I found that the uptake of N and P are most definitely limited by the availability of those nutrients, as well as K. This was particularly evident between days 9 and 11, as the nitrate levels stayed roughly the same, even without dosing N. By increasing the dosages of the other nutrients, eventually, nitrate went to 0ppm, and I resumed dosing it.

The knowledge learned in this two week test is going to be invaluable going forward with this tank. More to come on that in my next post…

3 Responses to “Figuring my Ferts”

  1. Auto-dosing Fertilizers - DIY Style-- Guitarfish Says:

    […] In my last post, I explained how I tested for two weeks to determine the proper amount of fertilizers my 40G tank needed to sustain healthy plant growth, and eliminate algae. With that knowledge in hand, I have now automated my dosing routine on this tank using a few readily available items to build a DIY auto-doser. I cannot take credit for this innovation, as I was following Jeff Ucciardo’s design, who adapted it himself from various designs posted on Aquatic Plant Central. […]

  2. Blaise Says:

    “Figuring My Ferts” would make an excellent GWAPA presentation (hint, hint). Other than Excel and Flourish, I’ve been afraid to start in with the NPK. I’m not even sure how to measure these parameters.

    I’ve recently come down with a severe case of beard algae on my bolbitis, java ferns, and anubias, so I’ve stopped dosing anything other than Excel and upped the volume of my water changes.

  3. guitarfish Says:

    Blaise, in fact, GWAPA is planning on doing a fertilizers presentation sometime later in the year, mostly done by Jeff U. We’re still in the process of setting the exact dates.

    Beard algae is one of the algae that seems to plague my tanks when everything else is seemingly going right.