Fertilizers: The more I research, the less I understand.

I have a 55 gal tank in which I am stocking several different species of plants. I went to the pet store today to ask about fertilizers and I did some online research as well. Now I am thoroughly confused as to what fertilizers I should use. My plants stopped growing and the leaves are turning yellow. All of my parameters are fine (ammonia, nitrites and nitrates). Currently, I am using Seachem Equilibrium and Seachem Flourish Excel. At the pet store I was told to add Flourish every day and to buy an iron supplement for my red plants. It seems that I will need to purchase several different bottles of fertilizers since I have not found a "universal" or an "all-in-one" fertilizer. I don't mind purchasing various bottles of nutrients as long as my fish will not die.

So I have a few questions:

1. Will using Flourish every day kill my fish?
2. What fertilizers should I use to introduce into my aquarium the necessary amounts of N, P, K, carbon, iron and many other micro and macro nutrients.
3. Do I need to buy CO2 cartridges to provide a source of carbon? Is there an alternative to using CO2?
4. Should I buy an iron supplement for my red plants?

I have read many posts on this forum, but, unfortunately, I am still uncertain as to which fertilizers to use. I would greatly appreciate any advice that you can provide.

BTW, I am a chemist so please feel free to use chemical names and chemistry terminology when needed.

Also, I have the following fish in my tank:
1. Twelve Red-Eyed Tetras
2. One Glofish Shark
3. One regular Plecostomus
4. One Bristle-Nose Plecostomus
5. I am planning on adding 10 Glofish Tiger Barbs.

Thank you.

 

Will using Flourish every day kill my fish?

Correctly dosed, it shouldn't do any harm.

2. What fertilizers should I use to introduce into my aquarium the necessary amounts of N, P, K, carbon, iron and many other micro and macro nutrients.

Personally I have had very healthy plants using osmocote water gardens, it has a good blend of NPK and micronutrients and it's very cheap too. You might have different results to me though, as I've always used it in conjunction with soil or some kind of nutrient-rich substrate. Also, if you go down the osmocote route i suggest you only use ~1-2 of the little spheres per gallon or so or it may cause an ammonia spike or algal bloom.

Do I need to buy CO2 cartridges to provide a source of carbon? Is there an alternative to using CO2?

You can do this, and it will help, but it can be costly (unless you go down the DIY co2 route). In my experience most plants do not require injected co2 to thrive, though some fast, hi-tech growers do, such as dwarf hairgrass.

4. Should I buy an iron supplement for my red plants?

No need. Your flourish should have iron in it and so does osmocote.

 

I pulled up some numbers
Here are the weekly cumulative doses of nutrients you would want to shoot for in an EI method tank vs. an ADA method tank

NUTRIENT (weekly dosage), ppm	EI	ADA
Potassium (K)	20~30	20~24
Nitrates (NO3)	15~20	1.5~6
Phosphates (PO4)	2~6	1.4~4
Magnesium (Mg)	5~10	undefined
Iron (Fe)	0.5~1

So, you will want to dose fertilizers (whatever type/combo works) and do water changes to arrive at these numbers every week. And even though they are not on the chart, don't forget trace nutrients. I dose traces to roughly the same levels as Iron (maybe a little less).

I prefer the EI method in tanks that are high tech and have a lot of stem plants, like Dutch style tanks.

I prefer the ADA method for pretty much everything else.

There are other methods too (like the Walstad method), but they are generally a little less spelled out and so don't always work the same for everyone.

You do not need to use CO2. But with CO2, you will be able to grow more species, and even the hardier species will grow faster and look more vibrant.

All plants need iron, including the red ones. If you want to get your red plants more red, add more light. I've also read limiting nitrogen can make red plants more red too.

 

Hi,

I know it can be mind boggling when you first start out. There are so many fettlizer products and then its deciding which will work best for your setup. Since your tank is 55g I would look into dry ferts. Cheaper and last longer.

Seachem liquid ferts are more water then ferts. Better for smaller tanks.

Also do you want low, moderate or highlight?
The more light, the faster plants grow and the more demand for ferts and CO2. Co2 is not necessary for a low/moderate light setup but it can be beneficial. If you are looking at wanting a lush planted tank with red plants then highlight and co2 injection with balanced fertilization.

You can purchase separate compounds at Green Leaf Aquariums. I dose them dry and use measuring spoons or you can make stock solutions.

Nutrient Dosing calculator: rotalabutterfly.com

Macros:
KNO3
KH2PO4
K2SO4

Micros:
CSM+B

 

I personally don't believe in liquid ferts. It's not that I don't believe they work, but rather I don't believe they do anything better than the cheaper alternative which is just feeding high quality nutritious food. Every food you put into the aquarium is fertilizer, so liquid ferts need to address something that your food cannot address.... So far, I have not found that thing...

I would love to see an experiment of a bottle of apple juice vs a bottle of Thrive C. I think apple juice may end up winning or having the same effect

Here's an older pic of my plants grown WITHOUT FERTS and WITHOUT CO2 injection:




This is a 75g grown from food for 35 cherry shrimp....

 

I personally don't believe in liquid ferts. It's not that I don't believe they work, but rather I don't believe they do anything better than the cheaper alternative which is just feeding high quality nutritious food.

There is an article on the website called T
entitled ""No ferts, no dosing, no CO2" planted tanks, how valid are they?" This article pretty much sums up why I think adding ferts+CO2 is the best, most reliable method. Your chances of creating a successful planted tank are much better if you add ferts & CO2. And, adding ferts & CO2 lets you grow more kinds of plants and create a greater variety of aquascapes.

Just look at tanks by ADA, Tom Barr, Josh Sim, George Farmer, Dennis Wong, Green Aqua, etc., etc. These sorts of tanks could not be achieved without the use of fertilizers.

 

There is an article on the website called The 2HR Aquarist entitled ""No ferts, no dosing, no CO2" planted tanks, how valid are they?" This article pretty much sums up why I think adding ferts+CO2 is the best, most reliable method. Your chances of creating a successful planted tank are much better if you add ferts & CO2. And, adding ferts & CO2 lets you grow more kinds of plants and create a greater variety of aquascapes.

Just look at tanks by ADA, Tom Barr, Josh Sim, George Farmer, Dennis Wong, Green Aqua, etc., etc. These sorts of tanks could not be achieved without the use of fertilizers.

Yes the key is injecting CO2. I was only talking about tanks that does not receive Co2 (In this carbon limited system, I believe there is little reason to add a bunch of ferts).

With the injection of CO2, the most needed element (carbon) for growth is satisfied. So in this scenario, you can then up everything else to extreme levels (light, nutrients) to essentially obtain the fastest growth biologically possible.

Although in this scenario, my point still stands, I don't believe liquid ferts are any better than adding more food. And for a proper fert + CO2 system I would recommend dry ferts.

 

Although in this scenario, my point still stands, I don't believe liquid ferts are any better than adding more food. And for a proper fert + CO2 system I would recommend dry ferts.

Perhaps. And, there is certainly a lot I don't know about all this. But, I have my doubts that fish food/poop is comparable to a comprehensive liquid fertilizer. In support of this, here is another quote from The 2HR Aquarist:

"Going the "No ferts, no dosing" route is basically a bet that your tap water has a good supply of essential minerals that make up for what fish waste cannot provide. Fish waste is not a wholesome source of nutrients- looks good in theory, works terribly in practice despite the claims of some books. Fish waste provides good amount of nitrogen and phosphates, but rarely adequate amounts of potassium & magnesium, and no fish I know excretes chelated iron as waste."

If the above quote is true, then I think it follows that adding a comprehensive liquid fertilizer, even in a tank without added CO2, is a more reliable/consistent way to successfully grow plants than to count on fish food/poop.

I would add that in my own experience I had a few planted tanks early on where I did not add CO2 nor ferts. I only had limited success in these tanks with some plants doing ok, others failing, and nothing looking completely vibrant. Once I switched over to dosing ferts, I have had much more success.

 

Perhaps. And, there is certainly a lot I don't know about all this. But, I have my doubts that fish food/poop is comparable to a comprehensive liquid fertilizer. In support of this, here is another quote from The 2HR Aquarist:

"Going the "No ferts, no dosing" route is basically a bet that your tap water has a good supply of essential minerals that make up for what fish waste cannot provide. Fish waste is not a wholesome source of nutrients- looks good in theory, works terribly in practice despite the claims of some books. Fish waste provides good amount of nitrogen and phosphates, but rarely adequate amounts of potassium & magnesium, and no fish I know excretes chelated iron as waste."

If the above quote is true, then I think it follows that adding a comprehensive liquid fertilizer, even in a tank without added CO2, is a more reliable/consistent way to successfully grow plants than to count on fish food/poop.

Comprehensive liquid fertilizers do not have minerals in chelated form though. Their description of iron is "water soluble iron" which doesn't mean anything. Same with magnesium, zinc, copper etc. None of them are listed as a form that plants can readily absorb which makes me think they are not. Also some nutrients cannot be dosed together because they will react and nullify eachother (eg. phosphorus and iron) so the concept of "Comprehensive" is flawed to begin with. Thus, to me they don't address the problem of replenishing essential minerals.

I don't think fish waste is a terrible source of nutrients either. It is only terrible because the food we feed is usually fish flakes which is high in nitrogen and phosphates and low in everything else. But if we feed things like kale, spinach, banana then they can provide (in theory) a lot of minerals that plants need....Although this is just from my own experience in attempting to achieve a no-dosing planted tank.

Anyways this is all just my own conjecture, I know people have tried a lot of tricks to get liquid ferts to work like iron gluconate (Flourish Iron) by mixing with acidic solution, dosing at night, storing in freezer and other ways.

 

Comprehensive liquid fertilizers do not have minerals in chelated form though. Their description of iron is "water soluble iron" which doesn't mean anything. Same with magnesium, zinc, copper etc. None of them are listed as a form that plants can readily absorb which makes me think they are not. Also some nutrients cannot be dosed together because they will react and nullify eachother (eg. phosphorus and iron) so the concept of "Comprehensive" is flawed to begin with. Thus, to me they don't address the problem of replenishing essential minerals.

I don't think fish waste is a terrible source of nutrients either. It is only terrible because the food we feed is usually fish flakes which is high in nitrogen and phosphates and low in everything else. But if we feed things like kale, spinach, banana then they can provide (in theory) a lot of minerals that plants need....Although this is just from my own experience in attempting to achieve a no-dosing planted tank.

Anyways this is all just my own conjecture, I know people have tried a lot of tricks to get liquid ferts to work like iron gluconate (Flourish Iron) by mixing with acidic solution, dosing at night, storing in freezer and other ways.

This is beyond what I know/understand. Is comprehensive liquid fertilizer a myth, or is it some sort of trade secret? I don't know. I would love to see a company do a breakdown of why they believe all these nutrients can be provided in the same bottle (and still be useful to plants) (and how they accomplish this). But, until I can find something like that, I tend to rely on the anecdotal evidence of my own experience and the experiences of others.

 

From my understanding, yes, no-fert no Co2 tanks can work, but its all based upon what your water already has in it. Somebody with tap water with a TDS of 0 will have no luck growing plants with no ferts no co2 as there are no building blocks for the plants to use. If somebody has a tap with a GH of 18 and KH of 18, there are lots of minerals for the plants to use, but not all. It just helps for them.

With that out of the way, here is my thought. Liquid ferts are something you use to 'bridge the gap' per say. What I will disclaim is that you shouldn't just dump into your tank ferts without any reason or sign to dose it. Getting back to bridge the gap, I mean that maybe your water has a lot of calcium and magnesium, but no potassium. Your plants will show signs of potassium deficiency and it is your job to recognize that. In reaction, you will start to dose potassium. If you got it correct, new growth over time will look good and things will go well, or they won't and the plants will show signs of a new deficiency, then you just rinse and repeat. Its simply learning. The best part is that once you develop your aquatic "Green Thumb" you never really lose it.

As for the basics of it, as it seems most have skipped over, I will explain them simple terms: Plants need three key components to live.
1) CO2
2) Nutrients (i.e. Fertilizers)
3) Light
Important Note: These are all directly correlated- meaning that you increase one the other need to increase to keep up. Ex: Increase light, you will need more fertz and CO2 to compensate.

What happens when your three components are not in-sync is that you get algae. Algae sees the opportunity to use of this excess component and takes over.

The best way to picture this is a triple venn diagram. Each bubble is a main component and in the center is your "Sweet spot" of prime growth.

What I would recommend to start is to start with lower light and shorter light periods. I mean like 50% light for like 6 hours a day. This means your light bubble will be smaller, so your plants use less CO2 and less fertz. If your plants aren't doing well overall I would bump up the light 10 or 20%, but it is just a starting point. With the smaller light bubble the need for the other two is decreased- thus you can dial in what you need. If you feel you have added too much or cannot keep track of what you have going on in the tank, do a large water change. To me thats like money going down the drain in fertz, but its a fast way to get back to square one. Not saying you have (or should) to do this, but its a good 'reset' button if you so choose.

Another thing is that CO2 is technically a fert and there really is no substitute for it so thats why many people put it into its own category. If you are looking at starting with it, you can get some type of water bottle and float it inside of the tank upside down anchored to the bottom do the mouth of it is facing down and the whole thing is floating there. Then take a canister of CO2 and fill the bottle, may want to let the air out beforehand so you know it is all CO2 in there, but regardless that is a cheap way of making a passive CO2 diffuser.

Disclaimer- I am actually not the greatest with plants, but this is my understanding. I never really put the work into it nor do I really understand the nitty gritty details of dosing. I am more of the *pours bottle* "Yep, that'll do 'er" kinda guy haha. I just have never taken the time or initiative to do any big research on my plants.

 

Plant fertilizers are very confusing and everyone has their own idea of how it should be done.

I’ve stopped trying to go with crazy complicated methods and I just use homemade osmocote root tabs for the substrate and Thrive complete fertilizer (there is one for high tech tanks with co2, one for low tech tanks without co2 and one for shrimp tanks).

I’ve had success with that and my plants were thriving without co2. I chose plants that were easy.