Dramatic TDS increase after fertilization

[Tistou]

Hello to everyone,

I would appreciate your insight on a situation I can't explain.
I have a 54 liter tank, with a fairly big plant mass (see photo below), no CO2 injection and medium light.

I keep fundulopanchax nigerianus killifishes in there so I try to keep the water as soft as I can. I use RO water that I remineralize to around 150microsiemens.
I just bought some TNC complete fertilization and dosed 3 ml wich gave me a 18 microsiemens rise. That sounded about right to me, but after noticing what I interpreted as deficiencies in my plants, I further dosed 5 ml. The conductivity rise after that was more than 80 micro siemens !
Using drop tests and rotala butterfly, I determined that even if there was only 30 liters of water in the tank, I would have had to dose 15 ml to achieve the results I read (0.6- 0.8 FE).
The only explanation I can think of is forgetting to shake the fertilizer before use and dipping my syringe in the deep part of the bottle but I'm not even sure that's how it works.
If anyone can enlighten me, I would appreciate not being afraid to use fertilizer

Thanks in advance !

 

[dw1305]

Hi all,
Welcome to UKAPS and nice tank, nice fish.

That sounded about right to me, but after noticing what I interpreted as deficiencies in my plants, I further dosed 5 ml. The conductivity rise after that was more than 80 micro siemens !
Using drop tests and rotala butterfly, I determined that even if there was only 30 liters of water in the tank,

You will get some rise in conductivity, plants take up nutrients as ions, and it is those same ions that conduct electricity. A <"relatively small addition of salts"> causes quite a large increase in electrical conductivity.

I use RO water that I remineralize to around 150microsiemens.

I'm going to say that is a lot more remineralisation than you need. If you add magnesium (Mg++) with your fertiliser? You don't need to add it with your remineraliser.

What do you add <"as your remineraliser">? Is it <"a product">? or <"dry salts">?

I would have had to dose 15 ml to achieve the results I read (0.6- 0.8 FE).

If you think you have <"iron (Fe) deficiency"> you can just add complexed iron and <"FeEDTA should be fine for you">.

Using drop tests and rotala butterfly, I determined that even if there was only 30 liters of water in the tank, I would have had to dose 15 ml to achieve the results I read (0.6- 0.8 FE).

You can't really test for plant available iron, If you did want an "empirical" test, you could use FeEDDHA and the <"pink tint"> method.

cheers Darrel

 

[Tistou]

Hi Darrel, thank you for the reply,

You will get some rise in conductivity, plants take up nutrients as ions, and it is those same ions that conduct electricity. A <"relatively small addition of salts"> causes quite a large increase in electrical conductivity.

Yes I expected a rise in conductivity, but I didn't expect it to be this high with the second dosing. I would have thought that dosing 5 ml would result in an increase of 1.6x the result of dosing 3ml.

I'm going to say that is a lot more remineralisation than you need. If you add magnesium (Mg++) with your fertiliser? You don't need to add it with your remineraliser.

What do you add <"as your remineraliser">? Is it <"a product">? or <"dry salts">?

I use JBL aquadur wich comes in the form of a powder. I think I do it mostly because I read here and there that RO water can't be used without remineralizing, mostly because of PH swings. From one of the post I read on this forum, I understood that PH readings in very soft water, at least with hobby test kits or pens, are not really relevant.
Would you suggest to not remineralize at all or to just remineralize less ? Like maybe to 50~80 µs ? TNC complete does have some magnesium in it but I don't see any mention of calcium.

If you think you have <"iron (Fe) deficiency"> you can just add complexed iron and <"FeEDTA should be fine for you">.

I think I didn't make the point I wanted to make. Sorry I try to be as clear as possible but it's difficult in a foreign language, even more so with such techical terms.
What I wanted to say is that after noticing the big rise in conductivity, I tested different parameters with a drop test. The results were approx. : 1ppm PO4, 0.6 FE, 15 NO3.
PO4 and NO3 could come from fish wastes. But, using the "dose to reach a target" function on rotala butterfly, I understood that to achieve this amount of FE, I would have to dose more than 20 ml tnc complete in 30 liters of water, wich I did not : I dosed 8 ml total after two 50% water changes in a row. I'm also pretty sure that my tank has more than 30 liters of water in it.
What I try to say is that for the dosage I used, I have way more nutrients in the water than I should have.

 

[dw1305]

Hi all,

I would have thought that dosing 5 ml would result in an increase of 1.6x the result of dosing 3ml.

It should have done, conductivity is a linear scale. I still use a conductivity datum, although I don't actually <"measure conductivity regularly"> any more.

I think I do it mostly because I read here and there that RO water can't be used without remineralizing, mostly because of PH swings. From one of the post I read on this forum, I understood that PH readings in very soft water, at least with hobby test kits or pens, are not really relevant.

Exactly that. If you stabilise pH you no longer have soft, acid water.

Would you suggest to not remineralize at all or to just remineralize less ? Like maybe to 50~80 µs ?

Yes, probably to 50 microS, you can carry on with the JBL Aquadur until it runs out. If you have <"hard tap water">? You can use that, it supplies 1 : 1 dGH : dKH (and is a lot cheaper).

I use JBL aquadur wich comes in the form of a powder.

I've just read the web page: <"JBL Aquadur">

....... The minerals of the carbonate hardness stabilise the pH level in the aquarium water and thus prevents a sudden drop in acidity and strong fluctuations. The carbonate hardness needs to be at least 4-5 ° dKH. If the values are lower you need to add JBL Aquadur.

It would be fair to say I'm less than impressed and that would actually stop me buying it (or any of the other products that JBL make).

...... Calcium chloride, calcium sulfate, magnesium chloride, sodium bicarbonate, potassium bicarbonate

These are chemicals that <"literally cost pennies">, and sodium bicarbonate (NaHCO3) is purely in there as an even cheaper filler.

TNC complete does have some magnesium in it but I don't see any mention of calcium.

It won't contain calcium (Ca) <"due to solubility issues">. Solubility is also why the Aquadur is a dry dosed powder, if it was a solution? The Ca++ and SO4-- ions would precipitate out as CaSO4.2H2O.

What I wanted to say is that after noticing the big rise in conductivity, I tested different parameters with a drop test. The results were approx. : 1ppm PO4, 0.6 FE, 15 NO3.

I wouldn't put my trust in them as values, PO4--- is likely to be <"in the right ball park">, after that probably "pick a number".

I actually have access <"to an analytical lab."> and staff who can use it, but we still get results that are sometimes questionable. It was actually the difficulty in getting accurate nitrate (NO3-) levels <"that led to the development"> (independently) of both <"Duckweed"> and Estimative Indices.

What I try to say is that for the dosage I used, I have way more nutrients in the water than I should have.

The great advantage of the Duckweed Index <"What is the “Duckweed Index” all about?"> is you just have to watch the plants and keep them in (limited) growth.

cheers Darrel

 

[Tistou]

Thank you very much for your answer.

I'm on my way to do a 50% water change and will follow your advice : I will aim for 50µs. It will take several WCs but I don't want to shock my fish.

I actually have read many of your posts on the duckweed index and it seems to be the smartest method when going lowtech. I have salvinia natans wich I understand is not the best to apply this method. I will try to get my hands on some Limnobium laevigatum, hoping it won't rot because of the humidity there is under the lid.

I think my aquadur will last for at least a year at the rate I'm using it. I certainly won't buy it anymore after reading what you wrote.

This forum also made me realize that premixed fertilizer are kind of a waste of money. I will most certainly end up mixing my own using salts if I can find any in France (which should not be an issue, I just did no research for the moment), but that's another topic !

 

[dw1305]

Hi all,

I think my aquadur will last for at least a year at the rate I'm using it.

That is an advantage of a dry salt straight away, you aren't paying for any added water.

I actually have read many of your posts on the duckweed index and it seems to be the smartest method when going lowtech.

I'm <"proud of it"> and it works.

I want people to keep planted tanks, both because I like plants (I'm a botanist by training), but also because they make fish keeping a lot easier and more enjoyable (for both aquarist and livestock). You don't need to worry as <"much about water quality"> (or water testing) and the plants do the <"heavy lifting "> for you.

. I have salvinia natans wich I understand is not the best to apply this method.

It is literally <"just the leaf colour">, if it had a grass green leaf? It would be equally as suitable.

This forum also made me realize that premixed fertilizer are kind of a waste of money.

It really depends how much you are willing to pay for <"ease of use">, in my case that isn't very much premium.

cheers Darrel