# Fish per Gallon Rule



## Cawafuoshi (Mar 24, 2021)

Hi natural scapers,

I passed up just the other week on the opportunity of trying the Walstad approach when re-scaping a small 2.5G tank because I didn‘t know about it. So, no soil but gravel, heavily planted nevertheless, ferts when needed. Just yesterday I incorporated her siesta lighting regime when reading about it on this forum. Keen on reading her book asap.

I‘m not going to tear down the current setup, but for future reference I would like to ask the following question:

Does the Walstad approach suggest a successful tank is suitable for a higher number of fish (just in theory; I am aware that factors other than ammonia toxicity might stress the fish) or do naturalists keep to the one inch of fish per gallon rule?

By the way, I am not planning on keeping fish in my „bowl“. I got a nerite for housekeeping and she has survived my care for 2 1/2 years and seems to keep going strong (judging it by the amount and frequency her eggs appear everywhere) 

So long.


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## jatcar95 (Oct 30, 2019)

Do people follow the inch per gallon rule? I am still a relative newbie, but I thought that had been deemed fairly inaccurate...but I could be incorrect.

People tend to stock Walstad's a bit on the heavy side. Assuming you have a heavily planted tank, the plants are able to handle the higher bioload, and the extra waste actually helps contribute back to substrate nutrients. 

It's probably still best to add things slowly, and watch the parameters as you increase the bioload.


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## Cawafuoshi (Mar 24, 2021)

Well, I‘m not sure if it‘s just a myth that has been busted. I thought as a general rule of thumb it‘s still taught in books or on forums.

If people successfully stock Walstads with a higher ratio, I‘d like to hear from them. Again, I‘m aware there are more factors why fish could fall sick and decease or just don‘t thrive. 

What are typical fish keeping mistakes in a Walstad tank?


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## ukamikazu (Jun 4, 2010)

Thought experiment:

Do six one inch guppies put the system under the same strain as a single six inch oscar? That's how I like to think about it.

I have found, for myself, in my personal opinion, my experience and my practice, that my Walstad aquaria do very well with slight overstocking but with very light daily feedings. Carbon is less limited and I've yet to encounter nutrient deficiencies and most importantly, the animals are (were. Thanks Winter Storm of 15 February, 2021!) healthy & active and engaged in breeding.

I really can't give you a guideline because everything I know and do is more intuited by my experiences.

What I believe, to answer your main question, are typical mistakes are underplanting, no siesta period, understocking and overfeeding. I also think, contrary to common practice, is that more laminar flow is better for avoidance of diatoms & cyanobacteria and the health of riverine species. Not a blast of water, just enough to make 80% or more of your taller plants sway ever so gently in the current. Also seems to keep them tidier.

Just my .02 dollars.


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## Cawafuoshi (Mar 24, 2021)

Thanks for your $  

In terms of bio load, that nerite of mine easily counts as a swarm of fish  

I already implemented the siesta period in my lighting schedule, Walstad or not.  It just makes sense by what was posted in terms of CO2 recuperation. It could be a coincidence, but my new plants added 9 days ago stopped melting, it seems.


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## jatcar95 (Oct 30, 2019)

Cawafuoshi said:


> If people successfully stock Walstads with a higher ratio, I'd like to hear from them.


In my 6.5g I currently have 6 lambchop rasboras (1" each) and a betta (2/2.5"). Also around 6 shrimp and a ton of snails. I don't measure my parameters regularly anymore, but when I did, ammonia was always 0. They are all healthy and active. The only thing I'd worry about in my case is the rasboras needing horizontal swim space, but I decided it was okay since it's a very long, narrow tank. I pretty heavily feed twice a day.


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## ElNaturalPurist (Feb 11, 2021)

Cawafuoshi said:


> Hi natural scapers,
> 
> I passed up just the other week on the opportunity of trying the Walstad approach when re-scaping a small 2.5G tank because I didn't know about it. So, no soil but gravel, heavily planted nevertheless, ferts when needed. Just yesterday I incorporated her siesta lighting regime when reading about it on this forum. Keen on reading her book asap.
> 
> ...


An El Natural tank shouldn't be more stocked than any other fish tank. That being said, the one fish per gallon of water rule doesn't apply in any type of fish tank for several reasons. For one, it doesn't account for larger fish (like an oscar as someone else mentioned). Also, it's just wrong. lol.

The correct ratio is 1" length of a small average fish per 12 square inches of surface area. For deeper bodied fish like angels or discuss the ratio should be 1" of fish length per 20 square inches of surface area. I've never stocked much above this in my any of my tanks, El Natural or otherwise.


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## johnwesley0 (Feb 23, 2021)

That 1" inch per 12sq." of surface area of water formula has been around since the Eisenhower administration and IIRC it presumed no mechanical filtration and was based on the idea that most of the tank's dissolved gases, including O2 and CO2 were being exchanged at the surface of the water. Nowadays, with widespread access to home testing, we know it is much more complicated than that. IMO, a well-planted tank has a lot of things that would have to go wrong before lack of oxygen ever became an issue. Chief among them is the possibility of too much ammonia. Ammonia is also a danger but it is produced from fish and plant waste within the tank itself. IMO, more fish have probably died over the years because a tank's nitrogen cycle crashed than ever died from lack of oxygen. So, the real question is: How often do you want to change your tank's water? There are people on this forum who do partial water changes every day of the week. Others can go for months with just topping evaporated water. It depends on your water's parameters.


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## zahtar (Sep 29, 2019)

Hello, welcome to the forums!

You can consider the fish per gallon thing only a starting point. I’d go slowly as Jatcar95 suggested. Introduce fish, measure ammonia and watch their behavior, as I guess you imply.

I’ve had aggression due to overstocking, despite measurements, water clarity and plant growth being fine. In a newer tank, I had cloudy water, despite plant growth, livestock behavior and measurements being fine. So, I conclude it is necessary to change things slowly and take care of how the ecosystem balances.

Regarding the main points in a walstad tank I’d say:

Choice of plants: the fast growers clean your water, the slow growers (cryptocorynes etc) take care of your substrate. So, if you don’t have enough fast growers, livestock could have a lower maximum limit. How much is too much? My thoughts mentioned above.
Plant survival: not every plant will do well in your tank. It sucks, but it is a fact that you’ll have to live with. Flip side: huge amount of plant choices, diversity is easy to achieve.
Plant competition: I am forming the impression that the fastest growing plants, leave little nutrients behind for the rest, so depending on how much of which type we have, this could also affect how some plants grow. Not sure about this, I would gladly be corrected. Diana Walstad has a chapter about allelopathy in her book, it might be the answer to this idea.
Buy plant tools: No need for expensive branded ones, just make sure they are stainless steel. Never pull up a plant to unroot it, you’ll make a huge mess. Never pull leaves or stems or anything with your hands or tweezers, use the scissors.

The last chapter in the book has a quick summary of the principles and main points, like no gravel vacuuming plus more that you should keep in mind. Starting with these, I can’t think of anything else that could be a real problem.


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## seadreamer90 (Jan 19, 2011)

I think it also depends on the tank shape. I have a 6-gallon that‘s 24 inches long with lots of swimming space (for a nano tank). It will hold more fish than my tall narrow 5-gallon even though the amount of water is close. In fact, I’m not sure I’ll have anything but invertebrates in the five.


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## Cawafuoshi (Mar 24, 2021)

Thanks for the welcome! My other message I posted earlier this morning must have coincided with the update and seems to be lost.

By chance I found a 9 months old thread that discussed the same topic, and Mrs. Walstad even had chimed in there confirming she once had a heavily overstocked tank.

While I believe ”one inch per gallon“ is a rule of thumb that, when followed, will play it safe, I can see where a successful tank could have a bit more fish in it if it contributes to a species overall happiness (let there be 7 danios schooling fish rather than just bare minimum 5, etc.)

My current setup really isn‘t suited for any fish. Heavily planted but only 10 liters/2.5 G. Unless there are micro fish that thrive under these conditions, this is more of an experimental tank for me to see which plants thrive in my water, under my light, and under my care.

I might transfer the whole setup at some point to a 5 or 10 gallon tank, but this is after I am sure what works for me best.

The snail has been a success so far. No starving and surviving various degrees of tank neglect in the past 2 1/2 years.


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## zahtar (Sep 29, 2019)

Yes, a 10 litre tank can help you conclude which plants do best and give you stock for a larger tank when you decide to build a larger one. In a similar volume (15L tank approx 12L net volume) I have a platy, a nerite, three amanos, and probably one (I'm afraid not two) rcs. Densely planted + floating plants do the job nicely.


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## ronnie (Feb 26, 2021)

There is a great post and discussion about this if you search the "El Natural" forum. Essentially, it is possible (overstocking)... but it depends a lot on the amount of successful plants growing, the age of the tank, and water parameters.

What I concluded was that it is possible, but has to be done with careful consideration and monitoring.

I encourage you to search older posts about it, and I can spend a few minutes trying to find the link as well. It was from a member who was breeding Endlers in the tank (if my memory serves me correctly). I may have searched "fish load," "bio load," or "stocking." Can't remember exactly.


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## zahtar (Sep 29, 2019)

I think you are talking about mysiak's tanks. Perhaps this one?









180l (~47gal) tank


Please say hello to my first tank ever, Juwel Rio 180 jungle. First photo taken after weekly pruning, second one is how it all started about 1.5 years ago :). I didn't know anything about Walstad method back then, but it is using similar principles (nutrient rich substrate, old "living"...




www.aquaticplantcentral.com


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## hoppycalif (Apr 7, 2005)

A few years ago I tried to make a better rule than one inch per gallon, and had to give up. But, if you wanted to do it, it is obvious that you would use mass of each fish (or volume), not length. And, possibly, area of the top of the tank instead of volume. That is why a 6 inch long fish is not the same as 6 one inch long fish. If my brain was still functioning as it once did I would tackle the volume of fish vs surface area of the tank. Wouldn't that be a fun project?


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## ElNaturalPurist (Feb 11, 2021)

johnwesley0 said:


> That 1" inch per 12sq." of surface area of water formula has been around since the Eisenhower administration and IIRC it presumed no mechanical filtration and was based on the idea that most of the tank's dissolved gases, including O2 and CO2 were being exchanged at the surface of the water. Nowadays, with widespread access to home testing, we know it is much more complicated than that. IMO, a well-planted tank has a lot of things that would have to go wrong before lack of oxygen ever became an issue. Chief among them is the possibility of too much ammonia. Ammonia is also a danger but it is produced from fish and plant waste within the tank itself. IMO, more fish have probably died over the years because a tank's nitrogen cycle crashed than ever died from lack of oxygen. So, the real question is: How often do you want to change your tank's water? There are people on this forum who do partial water changes every day of the week. Others can go for months with just topping evaporated water. It depends on your water's parameters.


Funny, I would say that the 1" per gallon was also around since his administration, but you do bring up an interesting point. But the fact remains that a 10" oscar is not going to be happy in a 10 gallon tank, no matter how many water changes you make to keep ammonia down. Both the 1" per 12 square inches and the 1" per gallon are just starting points. One needs to consider the needs of the actual fish as well. Bottom line: There is no hard and fast rule. Best we can really say is "It depends..." lol


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## tiger15 (Apr 9, 2017)

ElNaturalPurist said:


> Funny, I would say that the 1" per gallon was also around since his administration, but you do bring up an interesting point. But the fact remains that a 10" oscar is not going to be happy in a 10 gallon tank, no matter how many water changes you make to keep ammonia down. Both the 1" per 12 square inches and the 1" per gallon are just starting points. One needs to consider the needs of the actual fish as well. Bottom line: There is no hard and fast rule. Best we can really say is "It depends..." lol


1 inch per gallon rule works fine with small fish, but not with big fish. There have been studies in food fish industry on the relative mass of fish versus length. I recall the relative mass is species dependent but roughly proportional to the square of the length. If we assume square of the length is the relative mass, then a root mean square length per gallon would be a better representation of the 1 inch rule.

Here is how to calculate RMS length per gallon using a spreadsheet:

Square the length of each fish, tally the sum, divide the sum by the number of gallons, and then take a square root. For the 10" Oscar in a 10 gal example, the RMS length will be 3.162.


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## ElNaturalPurist (Feb 11, 2021)

tiger15 said:


> 1 inch per gallon rule works fine with small fish, but not with big fish. There have been studies in food fish industry on the relative mass of fish versus length. I recall the relative mass is species dependent but roughly proportional to the square of the length. If we assume square of the length is the relative mass, then a root mean square length per gallon would be a better representation of the 1 inch rule.
> 
> Here is how to calculate RMS length per gallon using a spreadsheet:
> 
> Square the length of each fish, tally the sum, divide the sum by the number of gallons, and then take a square root. For the 10" Oscar in a 10 gal example, the RMS length will be 3.162.


What?


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## ronnie (Feb 26, 2021)

zahtar said:


> I think you are talking about mysiak's tanks. Perhaps this one?
> 
> 
> 
> ...


Yes! Thank you! I looked and couldn’t pin it down. I wanted to review it again anyway.
The above linked thread is a great discussion on this topic.


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## mistergreen (Mar 3, 2007)

Overcrowed tanks can be overcome with more filtration.
If you're concerned with swimming space, it's obvious. Big fish need big tanks to swim around.


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## johnwesley0 (Feb 23, 2021)

ronnie said:


> Yes! Thank you! I looked and couldn’t pin it down. I wanted to review it again anyway.
> The above linked thread is a great discussion on this topic.


Yes, that is one heck of a thread, not the least because of the extraordinary photographs that accompanied so many posts. For our purposes, the discussion of bio load really begins in earnest at page 7 with the May 16, 2019 reveal that Mysiak has noticed some of his fish gasping at the surface in the morning, presumably after the CO2 level spikes during the overnight non-photosynthesis period. At that point, his 55 gallon NPT tank was stocked at nearly 400% per the usual "Rule(s)"!


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## mistergreen (Mar 3, 2007)

It's tricky in a dirt tank since you can't have major filtration. Fish pathogens are a big issue in overcrowded situations or overall health issues.


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## Cawafuoshi (Mar 24, 2021)

Thanks for the new responses.
Also, what a great read that linked thread is.

Technically, is it still a low tech tank? 

The amount of fish is really something.

I


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## dwalstad (Apr 14, 2006)

You can keep a lot of fish if you have robust plant growth, especially from emergent plants. (I scoop up excess floating plants from my filter-less tanks every couple of days.) Heavy filtration will result in acidic water and nitrate accumulation. In contrast to nitrifying bacteria, plant growth takes up ammonia without producing nitrates or acidifying the water.


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## johnwesley0 (Feb 23, 2021)

dwalstad said:


> You can keep a lot of fish if you have robust plant growth, especially from emergent plants. (I scoop up excess floating plants from my filter-less tanks every couple of days.) Heavy filtration will result in acidic water and nitrate accumulation. In contrast to nitrifying bacteria, plant growth takes up ammonia without producing nitrates or acidifying the water.


I would just like to add a word of confirmation here. I believe this why my next-to-last set-up crashed. My bio filter essentially shut-down once the water's ph dropped below 650 and no amount of water changes could get it back to neutral. I've had much better luck (so far) with the addition of emergent plants and a short-term visit from a calcium-rich rock to buffer the ph. I still have a fairly constant level of 10-20 ppm nitrate level which leads me to wonder where all the nitrifying bacteria is hiding out since I no longer have a filter? My substrate - such as it is - is pure gravel.


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## Cawafuoshi (Mar 24, 2021)

Thanks for all additional replies.

I set up a 5.5 gallon experimental tank. I went with Fluval Stratum although I assume, from what I’ve read, it is not necessarily “all natural” soil since Fluval is quiet about its composition.

It was again a matter of convenience. 

I‘m counting 12 species of plants, some names I need to research 

Any recommendations regarding stocking?

I‘m torn between Neon Tetras, Glow light Tetras or Danios. Or no fish at all. I think bio load is manageable with just one species but how about enough space for their swimming needs?

I won’t consider Chili rasboras et al since I would have to buy them online. I rely on my local petco or -smart.


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## Cawafuoshi (Mar 24, 2021)

dwalstad said:


> You can keep a lot of fish if you have robust plant growth, especially from emergent plants. (I scoop up excess floating plants from my filter-less tanks every couple of days.) Heavy filtration will result in acidic water and nitrate accumulation. In contrast to nitrifying bacteria, plant growth takes up ammonia without producing nitrates or acidifying the water.


Interesting! I thought heavy filtration in addition to plants would provide even more benefits and stability. Do you discuss this topic in your book?

I’m torn between the Kindle or hard copy edition. Is the Kindle one on par with the hard copy in terms of illustrations?

Thank you


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## johnwesley0 (Feb 23, 2021)

One thing I do not miss about running a filter 24/7 is the extra electricity. My daily kilowatt hours have decreased by 1.5 since I unplugged in January and has shaved about ten dollars from my monthly bill.


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## hoppycalif (Apr 7, 2005)

Cawafuoshi said:


> Interesting! I thought heavy filtration in addition to plants would provide even more benefits and stability. Do you discuss this topic in your book?
> 
> I’m torn between the Kindle or hard copy edition. Is the Kindle one on par with the hard copy in terms of illustrations?
> 
> Thank you


I have only the Kindle version, but I find it possible to use it as a reference. I prefer using a paper book because it is much easier to search for specific information, but it also costs more, and I quit keeping lots of books several years ago.


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## Cawafuoshi (Mar 24, 2021)

hoppycalif said:


> I have only the Kindle version, but I find it possible to use it as a reference. I prefer using a paper book because it is much easier to search for specific information, but it also costs more, and I quit keeping lots of books several years ago.


I made up my mind and ordered the hard copy.


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## jatcar95 (Oct 30, 2019)

DutchMuch said:


> jesus christ i cringed so hard reading this


Can I ask why? Does this seem too overstocked in your opinion?


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## DutchMuch (Apr 12, 2017)

jatcar95 said:


> Can I ask why? Does this seem too overstocked in your opinion?


Over stocked would be an understatement and the fact no one else commented on it here disappoints me and has now made me realize how unfortunately mis-informative everything has gotten here.


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## Cawafuoshi (Mar 24, 2021)

My worry is not so much the water quality in an all natural tank (assuming it’s stable) but the available room for fish to be happy enough.

While I agree that large tanks make up for heavy planting by offering enough headroom and horizontal swimming space, many Walstads on the tube are nano tanks, and it‘s quite impressive how much can be stuffed inside a cube or small long tank. 

If a fish‘s happiness could be measured by their willingness to breed, there are examples of that too in such cramped environments.

But I get the feeling people tend to overstock since they seem to get away with it.


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## jatcar95 (Oct 30, 2019)

DutchMuch said:


> Over stocked would be an understatement and the fact no one else commented on it here disappoints me and has now made me realize how unfortunately mis-informative everything has gotten here.


Are you more concerned about the parameters or the swim space for the fish? If you'd like to make constructive comments to contribute to the forum, that's great. But if you're really concerned about the quality of the forum, I'm not sure how adding snarky comments with no real information helps.


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## johnwesley0 (Feb 23, 2021)

I'll be honest with you. One of the adjustments I have had to make in participating in this forum is the focus on plants. When people talk "bio-load" they are, more often than not, talking about teeny-tiny shrimp or snails. I'm fascinated by the Walstad method and maybe one of these days I will invest in a glass tank once again and try my hand at creating a well-planted, dirted tank. But, for right now, I am just grateful for the knowledge gained from this forum that has allowed me leave my six glo-fish danios for a week without worrying about a filter tube falling out of place and flooding my apartment!


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## Cawafuoshi (Mar 24, 2021)

Book arrived today! Now I’m making good on my promise and read it thoroughly.


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## Cawafuoshi (Mar 24, 2021)

So, I wanted to update all of you that around 2 weeks ago I decided on some Glow light Tetras for the 5.5 gallon tank. This tank was seeded with old filter material and partially old water, deco (lava stone) and drift wood.

I bought the remaining 5 (I wanted 6) they had at Petco and went thru the whole process of getting them up to speed for my water chemistry and temp.

One died of, what I think it was, osmotic shock, the others have perked up real nice. No abnormal behavior so far.

At some point I want to get a 10 or 20 gallon long, and they will be the first ones to occupy it. Until then, I’m still experimenting with my plants. Vallisneria asiatica made the list, since it really takes off in both of our tanks now. The mosses seem to like it enough too. The vote on roughly another 10 plant species is still out. Hornwort especially is not that fast grower that I thought it was.


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## Noahlikesfish (Apr 17, 2021)

In my opinion, as long as you have a tank (this applies to any tank) where the fish aren’t stressed or fighting and there isn’t like 500 nitrates. (500 nitrates can still be OK in some cases. My friend who had a reef tank did like no water changes for 10 years had sea cucumbers sea apples and all this crazy stuff with like 500 nitrates, sadly the tank crashed because the sea apple died when his dad did a water change.) my theory is that you can have 2-3 nano fish (like a neon tetra) per gallon of water, or 1 normal fish which could be a varying amount of nano fish. (like a bosemani rainbow (depending on its load and waste release i would say it would be about 4 nano fish). I know one guy has like 120-ish nano fish in a 40 gallon long and it’s a high tech planted setup


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