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Ok… caffeine subject of the day… plant fertilizer, and your fish…

Magnum Man

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Jun 21, 2023
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Southern MN
Sorry, the title of the thread, kinda sounds like an informational lecture... really these are just questions, & topics that come into my head, as I'm consuming my morning caffeine, & watching my fish... I'm not trying to spout out knowledge, as much as I'm trying to induce discussion, so I can learn from it...

So, tagging off my thread "carbon, and fertilizer", from yesterday…

I quit using fertilizer a while ago, because I don’t have the tools available to test the levels, or even know everything a plant needs ( as far as chemicals ) and much of what we are adding for plants, is poison to fish, and my goal here is to make the best environment possible, for my fish… yes, plants better the environment for the fish, but I’m questioning the beautifully planted tanks, that many of us, are trying to achieve, and wondering if it’s really healthy for fish to live in those tanks, that require heavy fertilization …
If you are running a tank like that, do you have tools to measure your concentrations of specific chemicals??? Or know enough about the plants needs, to ensure the chemical cocktails, aren’t slowly building up chemicals, that the plants aren’t fully using, and thus need to be diluted out, with the water changing… before I gave up chemical fertilizers completely, I had started looking at single chemical fertilizers, to use instead of the general fertilizer cocktails... that's when I realized I didn't fully understand all the plants needs, and the fishes reactions to the variously added chemicals, & what, if any of these were actually in the fish wastes already... so at that point I dropped all added fertilizers...

I’m am able to maintain a planted tank, I’m just not able to keep some of the plants I’d like, as they weren’t thriving, without fertilizer supplementation… but there are some plants, that will thrive off of fish waste, and the normal minerals found in water change water ( my plants have to get by with less, as I’m using RO ), so my plants have to thrive off of fish waste only… and as I've worked through them, they are, so far…

Most of my tanks are heavily stocked… I'm rationalizing here… that doing so provides “more” natural fertilizer for the plants…

So how are you insuring, that you are providing a healthy environment for your fish, when adding chemical fertilizers???
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This interests me. In spite of the popularity of test kits, all we easily test for is ammonia. There's a great degree of trust in products we use.

I'm growing plants I could not grow for decades, since the advent of high quality LED plant lights for tanks. I use root tabs only. Do we generally go on a 'wing and a paryer' and blindly hope our ferts are fine for fish, or are there affordable and easily accessed tests?

I've always wondered when we test GH and DH, what the minerals counted are, for example. I have the exact same test kit hardness here as in my old house 800 km west. But here, I can grow plants I never could there, and vice versa. Najas barely survives, but water wisteria grows really well. In spite of what the test kits tell me, since I have the same tanks, same lights, same substrates, same no ferts - something is quite different.

I knew I should have taken that chemistry course.
Hello Magnum. You're one prolific poster! I used to use liquid, organic fertilizers, but I stopped and just fed my fish foods that contained nitrogen, phosphorous and potassium. I read that NPK was all the plants needed for growth. Now, I've gotten to the point I just change out a lot of water and let nature do whatever it wants. I've gotten somewhat lazy in my old age.

I think NPK, is the basic... but there are lots of other chemicals, minerals, and compounds available... and then how are the NPK introduced ( what Sulfate or other chemical forms are the NPK introduced )

there is a big market right now for aquarium fertilizers...

not to pick on any specific fertilizer, but I actually have most of a bottle of this in my cabinet... ( Seachem Flourish )
Listed ingredients... Potassium Chloride, Calcium Chloride, Copper Sulfate, Magnesium Chloride, Ferrous Gluconate, Cobalt Sulfate, Magnesium Sulfate, Manganese Sulfate, Boric Acid, Sodium Molybdate, Zinc Sulfate, Protein Hydrolysates.

& since this isn't a food, I bet a lot of them don't list their ingredients...

it goes way beyond NPK... and the bulk of the contents probably aren't actually listed on a lot of them... and looking at the listed ingredients above, several are Chlorides, & several are Sulfates... assuming the plants aren't using the Chloride part for example, on the Potassium Chloride, I don't think the fish like Chlorides, if the Plant uses the Potassium part, what happens to the remaining compound... does it combine with other Chlorides, or Sulfates or??? how many chemicals can we expose our fish to, & expect them to live a healthy happy life...

I just re-read the previous paragraph, & I sound like an organic hippy... sorry
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Locally, I can easily think of 3 "companies' marketing aquatic ferts. It's a big do it yourself, cottage industry, though I suspect the selling is less about profit and more about meeting people who are into plants.
A few years ago, we had an explosion of small breweries, rapidly cleaned up by the big corporate beer sellers. In the aquarium world, I expect the same thing will happen - a scene with small companies will flourish, but they'll be crushed, bought out or worn out.
It's fun to see, and it's pleasant to be able to support the small operators for as long as they last.
I’m am able to maintain a planted tank, I’m just not able to keep some of the plants I’d like, as they weren’t thriving, without fertilizer supplementation… but there are some plants, that will thrive off of fish waste, and the normal minerals found in water change water ( my plants have to get by with less, as I’m using RO ), so my plants have to thrive off of fish waste only… and as I've worked through them, they are, so far…

I am curious, what plants do you find thrives without fertiliser, and which ones have you found needs them and can’t do well without them?
Potassium Chloride, Calcium Chloride, Copper Sulfate, Magnesium Chloride, Ferrous Gluconate, Cobalt Sulfate, Magnesium Sulfate, Manganese Sulfate, Boric Acid, Sodium Molybdate, Zinc Sulfate, Protein Hydrolysates.

If this cannot change water hardness... My grand'ma pitch for the Orioles...

The problem could be that you add Calcium Chloride to your tap that is already very rich in it. or magnesium or potassium ???

In general aquaria from 2/3 to 3/4 of calcium vs magnesium is the "Golden ratio" at any concentration needed for any species... The other dissolved solids are nearly unknown with some exceptions that can be tested like, Phosphates, calcium, nitrates, iron... With your GH and KH you can guess what are your proportions of unknowns dissolved minerals and calcium.

With these results you can asses that: hypothetically "versus your total dissolved minerals that is already reaching the maximum tolerated by the species in question... You can still be low on calcium or magnesium.

But. Your idea lead me to try to use 100% RO/DI and only add a full dose of fertilizer and run the tests I have...
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The bulk of my plants are emergent terrestrials, but it’s still the same, only a little worse, as several terrestrial plants don’t really take to the water, and then of those, several won’t thrive without fertilizer…

For fully submerged plants, I’ve had the best luck with rhizome plants… I mostly have Java Ferns, but have begun to slowly experiment with more varieties… I particularly like this one… it’s an Anubis… this tank is 24 inches deep, and these are running about 20 inches tall… I’ve only had them for a couple months… we’ll see how they do in the long run…
As for emergents, I’ve had good luck with Lucky Bamboo, Chinese Evergreen, Peace Lily, Pothos, Philodendrons, and Hoya plants… I used to have several others, and still have some African Lilies, which are growing, but I would say, they aren’t really “thriving”… same with the Calathea’s, and I did try several varieties…

This Hoya is a new one for my tanks, but these are cuttings from a plant whose roots are 100 ish years old… ( originally my wife’s grandmother’s plant ) to early to tell for sure, but they can be kept a long time in a glass jar of water, so I’m optimistic… these have been here 4-6 weeks… they will grow long running vines, and flowers cute little white flowers
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I put my fiirst live plants into my tanks in about 2002. I have done it all at one time or another, This inluded a tabk with presurized CO2 and very high light levels. Today I keep a smaller variety of plants and do low to moderate lighting. Though it all there has been one consatnt and that was the fertilizer I used. While I started with a bottle of flourish and later on messed around with Seachem individual ones, my fertilizer of choise has been Tropica.

It used to be one comprehensive product which I bough in a 5 litre jug. Today they offer two lines and I have both. Tropical is one of the worlds largest producer of Aquarium plants. It used to be tone could not buy them in the USA because ouf laws required all live plants arriving into the country had to do so with their roots bare.

Things have changed over the past 20+ years. Tropica was bought out and they also becane cloning plants. I fihgured whatever ferts they were using was more than good enough for me.

Premium Nutrition without nitrogen and phosphor for aquariums with many fish- 6 mL a week per 50 L water is easily dispensed with the pump and ensures proper plant growth.
  • Contains iron, magnesium and vital micro nutrients
  • Does not contain nitrogen and phosphor
  • Suitable for aquariums with few or slow-growing plants and many fish

How to use the product​

Premium Nutrition is added every week when changing the water. The pump bottle dispenses 2 mL per push. We recommend 6 mL (3 pumps per 50 L water per week), but recommend that this is set in accordance with plant requirements. For example, pale leaves often indicate lack of nutrition, but can also be due to poor growth. Echinodorus bleheri will often show lack of micro-nutrients. Regular dosing with Premium Nutrition can restore green and luxuriant leaves. Note, however, that Premium Fertiliser is a fertiliser and not a medicine for dying plants.

It is recommended that minimum 25% of the aquarium water is changed every second week. If undesirable algae growth does occur, then we recommend increasing water change frequency (up to 50%) and planting additional rapid growth waterplants such as Hygrophila, Vallisneria and Egeria.

Specialised Nutrition with nitrogen and phosphor is easily and exactly dispensed with the included pump.
  • Contains nitrogen and phosphor for fast-growing and demanding plants
  • Also contains iron, magnesium and vital micro nutrients
  • Suitable for aquariums with many and fast-growing plants

How to use the product​

Specialised Nutrition is added each week when the water is changed. The pump bottle dispenses 2 mL per push.
We recommend 6 mL (3 pumps) per 50 L water weekly. However, we recommended that this is set in accordance with plant requirements. Specialised Nutrition contains, in addition to micro-nutrients, all essential macro-nutrients. The fertiliser is particularly suitable where plants display a lack of nutrition. However note that if algae growth starts, Specialised Nutrition will promote this growth.

Specialised Nutrition contains nitrogen (N) and phosphorus (P). Dosage must therefore be adapted to plant absorption rates, to avoid undesirable algae growth. Where signs of algae growth develop, reduce the dosage by 50% and increase water changing frequency by 50%. Changing the water not only reduces the concentration of nutrients in the water, but also removes algae spores, remnants and other accumulated elements from the aquarium water.

If you want some of the best information in terms of every aspect of planted tanks right from the horse's mouth: https://tropica.com/en/
You can view the site in German, French or Dutch as well as English.

Now, I do not believe there is anything in the fertilizers I use whch is harmful to my fish in the dosinglevels it is being used. I have also been using Flourish Excel in my planted tanks for over two decades and I see absolutley no evidence that is has done any harm to my fish. My clown loached have been one such fish and I have had two now for well over 15 years and lost one a while back which was about 22 or 23 year old. My sidthimunki loaches have almost as long a recod in their panted tanks going for almost as long as my older clowns. I have a colony or red cherry shrimp in a tank getting excel for at least a dozen years maybe more.

I have no test for any ferts. Plants show you what they lack by how they grow. Weekly 50%+ water changes prevent things from building up. What amount of ferts I dose depends on the mass of plants as well as the species and the stocking of any given tank. My substrate fertilizer of choice has been Jobe's fertilizer Spikes for Lush Ferns & Palms. These can be cut into an size piece one wants for use in a tank. But once inserted they should never be unearthed. If you do so, you will quickly earn your MBA (Mastered By Algae).

I took this from a thread on UKAPS.; The title is not so acciurate as the chart includes NPK on the bottom.

You can see what any plant if doing poorly and the above should help one know why. But, there is also this in post in the thread by somebody I lnow from Planetcatfish who is very big on having plants in tanks. On the UKAPs site he is listed as an sexpert.Hi all,
I personally find it maddeningly hard to diagnose deficiencies - there are just so much overlap between all the deficiency symptoms
Same for me, other than iron (Fe), <"I don't normally try to"> diagnose deficiencies. I just add a complete fertiliser and hopefully that gets the job done. Iron is the easy one, it causes chlorosis in new leaves (not mobile in the plant) and is much more likely in hard water.
It is a long thread but if you are interested: https://www.ukaps.org/forum/threads/plant-deficiencies-and-the-fe-experiment.71191/
that chart is pretty interesting, and informative...

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