Mixing Dry Ferts?

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Registered Member
Dec 18, 2020
New to this forum so, hello one and all.
I have set up my 240L tank with aquatic substrate, plants, rock and wood. CO2 is available.
The filter is external with heater.
The tank has been running for 3 days and so far, all seems OK (TOUCHING A LOT OF WOOD).
I am doing a 25% water change for the first week.
No fish have been added. Probably in the New Year.

I have read a lot about plant ferts and I am now pretty confused.
I have purchased a bottle of ferts to get me started as and when needed.

I also purchased: Plantex CSM+B, KNO3, KH2PO4 and K2SO4.
I understand what each compound gives to the aquarium plants its the amounts I am struggling with.
Can I mix the compounds in water let's say make up a 500ML solution?
I have read that most if not all the compounds are in the bottles you buy anyway and would be a lot cheaper!
If this is possible can you give the amount for each compound to add to the water.
Any help would be much appreciated.


Mar 29, 2005
You can mix the compounds in water.. however it is normal to keep micro and macro nutrients separate as they can interact with each other and make them less useful as fertilizers.

The amounts really depend on your situation, your water, specific plants and whatever else is in the water column.

Personally, though, I am a fan of the amounts found here https://gwapa.org/forum/viewtopic.php?f=7&t=152
Apr 2, 2002
New York
If i remember correctly from Tom Barr was this concept. You do a broad fertilization with the idea to make sure there is ernough of everthing being added in terms of macro and micro nutrients. because all tanks are different, any given tank will use a lot of some things and much ess of others. if no action is taken one ends up with nutrient deficiencies and nutrient excesses. Neither condition is good for the plants.

So what was suggested is doing two 50% water changes a week and dosing ferts afterwards. I could never manage to do two a week, but I was pretty religious about doing between 50& and 60% weekly and always redosed.

When I began I settled on the Tropica line of plants additives and was very satisfied with the results. I bought the products in bulk (5 litre size) and it last for some time. Over the years they changed the products name and packaging but it always worked great. But the prices rose over time and I decided to experiment with dry ferts. I even bough a triple bean balance for weighing things. I found this thread on the Barr report forums which claimed this dry fert formula would approximate the Tropica product How to make Tropica Plant Nutrition

Unfortunately, my plants did not agree with the dry mix and they showed a decline in growth and how they looked. Now I had a lot of dry ferts I no longer wanted to use. I bit the bullet and paid up for the Tropica. For a while I did a 50/50 mix of the Tropica and the dry mix. Eventually, I gave up the dry completely. The current availability of Tropica products in the states is awful. The largest bottle I can find is 300 ml for either the comprehensive or the micros. Fortunately, I can afford to pay this, but I groan every time I click submit for an order.

Unless you are very lucky, it will take you some time to find the right balance for your tank. The next thing is the dosing needs will change over time. Firstly, plants grow which means they need more food as they do. Then it's time for a massive prune and the plant load drops pretty sunstantially. Then what reamins needs less food. Next, many of us like to change the plants in a tank every now and then. We remove a species or two and put in something new. Different plants have different needs and changing plants may also mean one needs to adjust the ferts.

Life is never simple :p


Mar 29, 2005
^^ That was Estimative Index/EI

it works, but relies on a few things.. there are other methods to dosing also, EI basically makes sure there are no deficiencies, and relies on weekly water changes of 50%

it was promoted and written about here maybe 15 years ago.

my personal preference is to mix dry ferts into solutions, 1 for macro, 1 for micro, and dose with an authdoser, and change amounts as necessary. YMMV