Help Help me with fertilizer recipe please

[Art]

As I'm reseting my aquarium, I thought it would be helpful to get the collective assistance of the community with various aspects. This way, we can all learn from each other.

I reset my aquarium about a month ago and the plants have now settled in. I'm back to weekly ~50% water changes.

The facts

• Plants are OK but could be healthier. Some algae is beginning.
• I could really use your help in deciding on a weekly fertilizer recipe. Please assume CO2 is fine (1.3 pH drop) and lighting is also fine.
• My tap water has 3 ppm of K, .2 ppm of PO4, 22 ppm of Ca and 4 ppm of Mg.
• Plants are stems but not super demanding.
• My objective is healthy, growing plants.

My initial thoughts on weekly fertilizer

• NO3 - 20 ppm
• K - 30 ppm
• PO4 - 7 ppm
• Fe - .6 ppm
• Ca - 22 ppm
• Mg - 11 ppm

What do you think? OK for weekly dose?

 

[Zeus.]

Apart from PO4 your initial thoughts are very close to Full EI or Clives EI Target (ferts in abundance), think 3ppm PO4 should be plenty for your plants.. You are aiming at a Ca:Mg ratio of 2:1 which is very acceptable IMO, many aim for a Ca:Mg ratio of 3:1. I didn't do 3:1 with my tap water as the [Ca] was about 100ppm so I would've needed to go for about 30ppm Mg which I thought was unacceptable as it would increase the gH even more and I had very hard water to start with.

The trouble with using a water companies water report for Ions and Cations is that the parameters change by the month, as farmers fertilise their fields. My Local water company use to blend the water also to keep it in line with EU regulations

 

[Art]

I'm in the city and the aquifer that they pull from isn't impacted by run off. Thankfully, we have a relatively active beer brewing community down here and they've tested the water throughout the year and confirmed no real swings in what the water company is reporting.

Now I need to convert this over to a daily dose.

 

[Art]

I've used the IFC Calculator to figure out how much to add to my 1000 ml container so I can add 15 ml daily. Really cool stuff..

Now, let's say I do a water change once a week of 50%. The auto doser is going to continue to add 1/7th of the above numbers daily. Would you recommend adding any dry fertilizer right after the water change (say 50% of 1 day's worth) or not necessary?

 

[Burr740]

As I'm reseting my aquarium, I thought it would be helpful to get the collective assistance of the community with various aspects. This way, we can all learn from each other.

I reset my aquarium about a month ago and the plants have now settled in. I'm back to weekly ~50% water changes.

The facts

• Plants are OK but could be healthier. Some algae is beginning.
• I could really use your help in deciding on a weekly fertilizer recipe. Please assume CO2 is fine (1.3 pH drop) and lighting is also fine.
• My tap water has 3 ppm of K, .2 ppm of PO4, 22 ppm of Ca and 4 ppm of Mg.
• Plants are stems but not super demanding.
• My objective is healthy, growing plants.

My initial thoughts on weekly fertilizer

• NO3 - 20 ppm
• K - 30 ppm
• PO4 - 7 ppm
• Fe - .6 ppm
• Ca - 22 ppm
• Mg - 11 ppm

What do you think? OK for weekly dose?

What is your water change volume and frequency? Those fert numbers really mean nothing without knowing that too

For example doing 30%/week its a whopping amount. For 75%+ its pretty lean

 

[Art]

50% per week, @Burr740.

 

[Art]

I'm still curious about manually adding fertilizer the day of the water change. I guess the question goes to stability of nutrient availability over the week.

I am providing the tank an extremely even amount of fertilizer every day of the week. However, on water change day, I take out 50% of the nutrients in the water because I do a 50% water change. Now the daily amount in the water column will start at 50% then slowly climb for 7 days until it drops again by 50% on the next water change day.

I am really not good at math but, to me, it seems I'm on a decreasing amount of nutrients in the water over time. If I manually add after a water change, then this is not the case.

 

[Burr740]

50% per week, @Burr740.

I think those numbers are about right

Mg is a little high, or to put it differently you dont need that much ime. My tap comes with 30-35 ppm Ca and 4-6 Mg. Its what Ive always used in all the tanks. Ive spent long periods of time running different levels of Mg, all the way up to 20 down to just whats in the tap. And this is with anywhere from 6 to 12 tanks going at the same time, some sand, some soil, different KH, etc

I never noticed anything specifically that adding more helps. And up in the 15-20 range plants seem to have a harder time getting enough K. This would coincide with Mulders chart and Ive seen it happen first hand, repeatable. I cruised at around 10 for a few years by adding an extra 5

About a year and a half ago I stopped adding any extra, just the 4-6 from tap along with the 30-35 Ca. Plant growth across the board has never been better. Not that lower Mg helps anything just the point that more isnt needed. We've all seen the crop studies with the 3:1-2:1 ratios. Thats why I started adding it to begin with 12 years ago like so many other hobbyists

But Ive found more often than not these ideal ratios from crop studies dont always apply to our underwater plants. Fe:Mn is another example. Personally with Mg I would err on the low side because it really doesnt matter and too much can start affecting other nutrients

In your case with 22 ppm Ca Id just go with the 4 thats in your tap. Also you may want to raise Ca into the low 30s. 22 might be enough but quite a few plants will do better with more, Rotala sunset and Florida come to mind, downoi, AR

About your water change dosing question. Youre exactly right and thats why daily dosing, especially macros, is not ideal if youre doing more than say 25-30% water changes. Because like you said its a big drop and takes a long time to catch back up in daily dribbles

Even with 50% I like to dose extra macros right after then a couple smaller doses through the week. Say 50% of the weekly total post wc, then 2x 25% through the week. If youre set on daily with an autodoser Id make a solution (or dry dose) to add about 50% of the weeks total after the water change, then you can daily the rest of it out in equal doses. That'll be a much more consistent water column

This is all just my personal phylosophy based on my own anecdotal experiences and what happens in my tanks. Others may have a different opinion or experiences

 

[Hanuman]

I'm still curious about manually adding fertilizer the day of the water change. I guess the question goes to stability of nutrient availability over the week.

I am providing the tank an extremely even amount of fertilizer every day of the week. However, on water change day, I take out 50% of the nutrients in the water because I do a 50% water change. Now the daily amount in the water column will start at 50% then slowly climb for 7 days until it drops again by 50% on the next water change day.

I am really not good at math but, to me, it seems I'm on a decreasing amount of nutrients in the water over time. If I manually add after a water change, then this is not the case.

Front loading allows for greater stability week after week as you don't get significant drops in fertilizer concentrations in the water. Below is a quick dirty simulation of 3 scenarios. It is assumed in these scenarios that the current PPM of the water is 30ppm and plant uptake is 3ppm (3ppm is just a random number as it could be anything depending on the plant mass):

1. RED - Dose 30 ppm once a week with a 50% WC weekly.
2. GREEN - Dose 10 ppm three times a week with a 50% WC weekly.
3. YELLOW - Dose 4.2 ppm daily with a 50% WC weekly.


You can clearly see what happens when dosing small amounts every day and doing massive WC changes. PPM concentrations drops with time. OFC this does not account for fish waste produced and whatever is in the soil and other factors but it shows you that if you don't replace what you remove from the water colum then you end up in a downward trend and this becomes more pronounced as the plant grow and require more nutrients.

I agree with @Burr740 My experience is that combining a 50% front loading and a bi-weekly (or three times) dose provides the most stability in the longer term with the least amount of ppm drops after a water change since you are adding mostly what you removed.

 

[Zeus.]

Was going to post about front loading myself. Makes sense IMO

 

[Art]

If youre set on daily with an autodoser Id make a solution (or dry dose) to add about 50% of the weeks total after the water change, then you can daily the rest of it out in equal doses. That'll be a much more consistent water column

Thanks @Burr740, your experience is showing. I don't have a choice but to use the auto doser given my travel schedule. I do think, however, that I can make it do something like what you suggest.

I guess the point is that consistency of nutrient level is important.

 

[Art]

Front loading allows for greater stability week after week as you don't get significant drops in fertilizer concentrations in the water. Below is a quick dirty simulation of 3 scenarios. It is assumed in these scenarios that the current PPM of the water is 30ppm and plant uptake is 3ppm (3ppm is just a random number as it could be anything depending on the plant mass):

1. RED - Dose 30 ppm once a week with a 50% WC weekly.
2. GREEN - Dose 12.85 ppm twice a week with a 50% WC weekly.
3. YELLOW - Dose 4.2 ppm daily with a 50% WC weekly.

View attachment 5935

You can clearly see what happens when dosing small amounts every day and doing massive WC changes. PPM concentrations drops with time. OFC this does not account for fish waste produced and whatever is in the soil and other factors but it shows you that if you don't replace what you remove from the water colum then you end up in a downward trend and this becomes more pronounced as the plant grow and require more nutrients.

I agree with @Burr740 My experience is that combining a 50% front loading and a bi-weekly (or three times) dose provides the most stability in the longer term with the least amount of ppm drops after a water change since you are adding mostly what you removed.

Thank you for the work and the easy to understand chart. The impact is clear and surprising in how quickly the levels drop dramatically. How did you make that chart?

It looks like front loading is the way to go with a couple of other doses during the week.

Question: would you treat micros the same way you would treat macros in this scenario?

 

[Zeus.]

Question: would you treat micros the same way you would treat macros in this scenario?

Micros best done as normal few times a week or daily - with Micros you are only adding very small concentrations so overall TDS doesn't change that much, Plus frequent is better as some micros (PO4) can interact with other ions/cations over time, so frequent doses keep them available to the plants esp in a high tech setup - well that's the theory

 

[Art]

Thanks. So I would add micros daily and only front load the macros?

 

[Zeus.]

Thanks. So I would add micros daily and only front load the macros?

Yes, or add bulk of Macros after WC and a few much smaller Macro doses during the week. Hani has more experience with front loading, as I don't have a active high tech tank ATM - just low tech ticking over.

 

[Hanuman]

The impact is clear and surprising in how quickly the levels drop dramatically.

That is dependant on the plant uptake and the amount of WC. The higher the uptake and the bigger the WC the more dramatic it is.

How did you make that chart?

With a calculator called Zorfox's Planted Tank Calculator.

Question: would you treat micros the same way you would treat macros in this scenario?

Zeus answered on that front. Same for me, no. Just dose daily.

Hani has more experience with front loading,

I used to do all sorts of front loads. 50%, 25%, 100%. You name it. I think best was the 50% + 2 or 3 additional smaller doses.
Only problem is you can't be doing this with urea. Dosing too much of it at once can be problematic. Urea is best dosed in smaller amounts regularly. At least that's my experience.

 

[GreggZ]

As others have said stability is key. Plants don't like change.

For many a large macro dose and two more doses during the week keeps things level. For me with my higher fish load I dose all macros (front load) right after a water change.

I don't test often but when I do it's almost always about the same........which is a good thing.

Here's a link to an earlier post of mine with my thoughts on front end loading. And there is one a few posts up from that one about accumulation.

GreggZ Front Loading Macros

What is best depends on the water change percentage and frequency and the fish load.

For me I have been front loading for years as it makes things very easy. I dose my RO tanks and fully dosed water is pumped into the tank after every water change.

 

[Burr740]

Agree micros can be daily as usual, they dont need front loaded

 

[Yugang]

Regarding front dosing versus daily dosing there is no good answer for all.

• If we lard on dosing, much more than plants consume, then front loading gives best stability between WC. In this case daily dosing would result in accumulation over time, and a drastic reset with WC.
• If we dose close to what plants consume, or even less than plants want to consume, then daily dosing would be best. In this case front dosing would result in a gradual decline of nutrients between WC, and a bump when dosed at WC.

So depending on plant consumption versus dosing (of course the argument goes for N, P, K, micros independently), the answer is anywhere in-between. If we really care, and have no knowledge of plant consumption, then more frequent water change, daily, is the best approach to keep nutrients stable.

 

[Burr740]

Theres no way to really account for plant uptake, even with accurate testing. Because uptake changes along with plant mass and the plant mass changes all the time, esp in stem heavy tanks with big light. Probably safe to say the avg tank like that eats 1-3 ppm NO3 per day, between freshly trimmed vs overgrown and needing one. Thats a considerable difference in weekly totals

Also not everything can be dosed for consumption, NO3 and micros probably the only ones. Plants arent eating through 30 ppm of Ca in a week, or K or even PO4. I had icp done one time by a friend who can do it at work. Post water change, mid week and weeks end, Ca barely moved a couple ppm

But theres something important about having a certain concentration present. Probably realted to nutrient interactions or the +/- balance of ions