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What plant fertilizer does fish poop provide ?

anewbie

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What specifically does fish poop provide in terms of fertlizer and is all fish poop created equal ? Do live bearers provide more or less of something than cichlid. Plant eaters, meat eaters and omi have an impact and type of digestive track (pleco for example i believe digest food differently than guppies).

It is a bit of a long winded question but i couldn't find any obvious discussion that talks about such. I am curious in part because i have one specific low tech tank that seems to grow plants quite a bit better than my other low tech tank and at times compete against the high tech tanks.
 

Nick potts

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Bigger fish or lots of fish = more and bigger poop. Specifics of fish poop analysis I can't help with 😂

In terms of nutrients, it mostly just nitrate that they provide i believe, from the breakdown from ammonia - nitrite - nitrate.
 

Nick potts

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In a planted tank, just assume they provide nothing, and fertilise on that basis.

True enough for most tanks, especially heavily planted ones, but with enough fish, or very large ones it is possible for them to provide more than enough NO3
 

tiger15

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Fish poop do not provide balanced nutrients, typically rich in nitrate and phosphate, but short of potassium and bio available iron. Your source of water can also make a difference on whether you have adequate calcium, magnesium and other micro nutrients that cannot be count on supplementation from fish poop.
 

three-fingers

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Fish poop can provide everything plants need, as fish food and tap water contain all the elements nessesary to grow plants. Many people keep planted aquariums with no fertiliser added or water changes (such as Walstad style tanks), the plants just grow much more slowly compared to tanks with added fertiliser, some species may not grow well at all depending on the other water stats and available light though.

However if your goal is healthy plant growth, you should just add enough of everything in the form of plant fertiliser to rule out the possibility of plant nutirent deficincies, which can obviouly lead to poor plant growth and lots of algae as a result.

Look at the chemical make up of the fish foods you are feeding the fish if you want a rough idea of what nutrients your fish are providing via poop - but don't count on these to actually be available to your plants, bioavailability depends on too many in-tank factors that are difficult to predict or measure.
 
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tiger15

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Fish poop can provide everything plants need, as fish food and tap water contain all the elements nessesary to grow plants. Many people keep planted aquariums with no fertiliser added or water changes (such as Walstad style tanks), the plants just grow much more slowly compared to tanks with added fertiliser, some species may not grow well at all depending on the other water stats and available light though.
This is a fallacy, and is unfortunately published in books. You have to be lucky to have your tap water in conjunction with your fish food (source of poop) to provide all balanced nutrients. If you review aquaponic guidances, they recommend supplementing potassium and iron that are typically deficient in fish poop, and calcium and magnesium if the water source is soft. Rarely a healthy plant mass can be sustained long term without nutrients supplement.
 

zozo

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three-fingers

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This is a fallacy, and is unfortunately published in books. You have to be lucky to have your tap water in conjunction with your fish food (source of poop) to provide all balanced nutrients. If you review aquaponic guidances, they recommend supplementing potassium and iron that are typically deficient in fish poop, and calcium and magnesium if the water source is soft. Rarely a healthy plant mass can be sustained long term without nutrients supplement.
It's not a fallacy at all, you are just misconstruing what I've stated ;).

Every element essential for plant growth is present betweeen fish food and tap water, you don't need to add more unless you want to avoid any particular element being a limiting factor to growth. But without adding any special fertiliser, all of the elements needed are still there and can be more than enough for healthy plant growth with the right combination of plant species and lighting intensity.

I'm very familiar with hydroponics, however that is a different game to keeping a planted aquarium. In aquaponics, you are not aiming for healthy algae-free submeresed plant growth - you are simply aiming to maximise the dry weight of tomatoes or whatever else you may be growing above the water ;). Also in aquaponics, the plants have the aerial advatage due to growing emersed, which means CO2 isnt a limiting factor, and they can gow faster which would result in a higher nutirent demand. If the aquaponic set up is outdoors, it's also going to be blasted with way more sunlight, creating way higher nutrient demand than any artificially lit aquarium.

It's very easy to set up an aquarium with healthy plant growth and no added fertilisers, it's also easy to set up an aquaponic set-up where the fish poop provided all of the nuturients the plants need without additional fertiliser. In most cases, if you add extra iron, K, etc. you will get a higher dry weight of whatever crop you are growing aquaponically but you don't have to. Many with hydroponic set-ups just add more fish food or fish.
 
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tiger15

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It's very easy to set up an aquarium with healthy plant growth and no added fertilisers, it's also easy to set up an aquaponic set-up where the fish poop provided all of the nuturients the plants need without additional fertiliser. In most cases, if you add extra iron, K, etc. you will get a higher dry weight of whatever crop you are growing aquaponically but you don't have to. Many with hydroponic set-ups just add more fish food or fish.
I haven't found it easy. My set up is essentially a hydroponic system with inert substrate and heavy bio load. Within a month of startup without dosing, I found holes in leaves, distorted and stunt growth, manifesting nutrients deficiency notwithstanding heavy feeding to my largely cichlid population. The deficiencies soon go away after I started dosing.

Aquaponic of emerged plants is easier than submerged plants as the former don't have to compete with algae and have unlimited CO2 access. Dennis Wong explains convincingly why no dosing tanks rarely work in practice.
 

three-fingers

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Let's be clear I'm not advocating avoiding fertilisers for any reason, just clarifying that fish food and the water do contain everything needed for plant growth and extra fertiliser simply is not nessesary for a planted tank. Adding fertiliser obviously makes it easier, but I totally would disagree no-dosing tanks rarely work in practice. It's quite easy to find examples online and in books, though it's a less popular method of maintaining a planted tank these days, since we understand more about fertilisation. In the past, most people simply incorrectly thought more nutrients=more algae and tried to limit many nutrients.

I'm sure Dennis Wong's article raises many excellent points that have reverberated with your struggle to maintain healthy plant growth without extra ferts (I've not read it, and you've not linked it), but I'm also fairly sure he never once stated it's a fallacy that fish food and tap water contain all the essentuial elements plants need. If he did, he's simply incorrect.

I'm sorry to hear you haven't found it easy...but that's just the case for your particular set up. If you don't find it easy, that's not a problem, it's generally better to add fertiliser anyway...no reason not to! If you fancy setting up a no-dosing tank in the future out of curiosity, I and many others here would be happy to help reccommend optimal plant species, substrate, light timings, etc. I promise it's not actually difficult, it's just more trial and error unless you are lucky, experienced or have been given good advice.
 

tiger15

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Let's be clear I'm not advocating avoiding fertilisers for any reason, just clarifying that fish food and the water do contain everything needed for plant growth and extra fertiliser simply is not nessesary for a planted tank. Adding fertiliser obviously makes it easier, but I totally would disagree no-dosing tanks rarely work in practice. It's quite easy to find examples online and in books, though it's a less popular method of maintaining a planted tank these days, since we understand more about fertilisation. In the past, most people simply incorrectly thought more nutrients=more algae and tried to limit many nutrients.

I'm sure Dennis Wong's article raises many excellent points that have reverberated with your struggle to maintain healthy plant growth without extra ferts (I've not read it, and you've not linked it), but I'm also fairly sure he never once stated it's a fallacy that fish food and tap water contain all the essentuial elements plants need. If he did, he's simply incorrect.

I'm sorry to hear you haven't found it easy...but that's just the case for your particular set up. If you don't find it easy, that's not a problem, it's generally better to add fertiliser anyway...no reason not to! If you fancy setting up a no-dosing tank in the future out of curiosity, I and many others here would be happy to help reccommend optimal plant species, substrate, light timings, etc. I promise it's not actually difficult, it's just more trial and error unless you are lucky, experienced or have been given good advice.
The link to Dennis Wong’s article is in Post #7 if you missed it.

In addition to my failed experiment on my no dose high tech tanks, I also experimented Walstad set up in my zero tech shrimp bowlS which I described in another thread.


Initially, I only made up evaporated water with no dosing at all, relying exclusively on shrimp feeding, poop and organic soil. The plants were doing fine for about 8 months and started to decline, notably the yellowing frogbit which is an indicator of nutrients deficiencies as floater has unlimited access to light and CO2. The deficiencies were corrected only after I started doing regular water change by replacing with my high tech tank water thereby getting secondary dosing.
 

three-fingers

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The link to Dennis Wong’s article is in Post #7 if you missed it.
Ah, I did totally miss this, sorry! My mind registered this as the same link Zozo posted for some reason 😅.

Having now read it, I can say with certainty Dennis Wong never implies it's a fallacy that fish food and tap water provide all the nutiritents plants need. He simply explained that in his opinion and experience - specifically within the context of the goal being the "optimal growth" of plants - these two sources often don't contain enough . Which basically comes down to how you define "optimal", usually this means unlimited by nutrients (like with EI dosing).

I totally agree and echo his sentiment that "Given the cheap price of liquid fertilizers, there is really no reason not to dose minerals".
 
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