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self-sustaining aquarium

6K views 43 replies 9 participants last post by  Flear 
#1 ·
if there is a more appropriate place for this thread, please advise and move :)
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how many people here are interested in the idea of a self-sustaining aquarium ?

those that have thought about it, but not tried. ?
those that have tried, maybe it failed, (what was learned) ?
those that have curiosities that may need to be considered at addressing such an idea. ?

-first, looking for other minds with similar interests, or those who have learned a thing or two from the attempt
 
#2 ·
I have an interest in this area myself. I can't say that I understand how plants fit into the nitrogen cycle very well, but I will have a tank set up in the next couple of weeks that will use plants exclusively as the filtration system.

It is a small BW aquarium with a very low PH that I am stocking with tiny nano fish. As I understand how these work, you can't grow out nitrifying bacteria because of the low PH, so you have to use plants.

I'll be using Hornwort, planted wisteria, frogbit and duck weed as the plants. All fast growing, with the nutrient hog Hornwort as the center piece. This will be my first attempt at something like this.
 
#3 ·
will read more later when i have more time

plants can either take in ammonium directly (if your pH is low) or they will take in nitrates (costs the plants more energy to process as they run nitrates backwards through the cycle till they have ammonium

ammonia is not the same as ammonium here

as the plants will suck back nitrates, this is removed from the equation of any reason for water changes, nitrates will not build up, ... unless you are overstocked and/or don't have enough plants to handle the amount of nitrates being produced in your tank
 
#4 ·
low pH screws up the nitrogen cycle

all potential ammonia is converted to ammonium
ammonium in non-toxic to fish, ... not low, but non-toxic, ... you could have lots of ammonium and still be fine

a low pH being under 6.5.

plants can absorb directly ammonium and use it, and are very happy to do so :)

test kits don't test ammonium, only ammonia, so how much you have in your tank becomes a mystery, ... and the plants are just happy it's there.

---

word of warning, ... if your pH shifts though, ... say it reaches 6.8, ... all your fish die due to ammonia spike.
 
#5 ·
Most test kits do actually test for ammonia/ammonium. The most common one in this hobby - API 'ammonia' test does test for both. This is considered a total ammonia test (NH3/NH4+). You can get tests that just test for free ammonia which is just NH3.

Self sustaining is not possible since a natural ecosystem itsn't self actually self sustaining either. There are a massive number or reason it would not work long term. Also attempting it would severely limit what you can do and keep.
 
#8 ·
APIs test is for total ammonia - both NH3 and NH4 are reported on that test. It does not differentiate between them. Total ammonia is the idea ammonia test to use since NH3 and NH4 don't really matter apart from they should not be in a stable tank. If you add prime or something its going to lock all ammonia as ammonium for 1-2 days so again regardless. You want to know total ammonia since even the mostly non-toxic ammonium should not be present in a stable aquarium. Ammonium is a precursor to nitrite same as ammonia, if the biofilter gets ammonium it will still produce nitrite. Thus we care most about total ammonia not free ammonia.
 
#7 ·
I must apologize as I jumped into this thread a little too quickly.

My knowledge at this point is pretty much limited to the front end of setting up and cycling the aquarium. What is lacking for me is knowledge of how to sustain the aquarium. By that I don't mean the usual maintenance and water change tasks. I mean the care and maintenance of the eco-system... plants, nutrients, and so forth. I understand very little of what give and take is happening among the plants, bacteria and fish that inhabit the aquarium, and what role I play in encouraging and maintaining that balance. Also in terms of what tools do I use while fulfilling the role of care taker.

My tank I described above is the first where I will have to use plants alone for the filtration. I am very interested in how to help that along so it works well. That is far from creating a self-sustaining environment, which I am quite certain is beyond my grasp right now.

I am going to follow this thread, though, as I am certain to learn a thing or two as it unfolds.
 
#9 ·
If there is no bacteria, then there is no nitrate.
A pH 6.5 is not low enough to slow down the bacteria.
Even if your test show zero ammonia/ammonium, zero nitrite and zero nitrate, you'll still have to do water changes. Plants will need minerals (over time, they will deplete). Also, fish release pheromones into the water. Pheromones accumulate over time, signaling "crowding". Fish stop growing.
Water evaporates, needs replaced, unless it rains. pH keeps dropping because of organic acids. Some fish can go as low as 3.
Too many things to think about...
 
#10 ·
plants can be used alone to ensure nitrates are at acceptable levels, ... if you have lots of plants and/or low bioload.

some fish this alone will provide all that's necessary that you don't have to change the water.
other fish this is a recipe for heartbreak to come home to dead fish.

different fertilizer styles change things.
some fertilizers are based on ensuring nothing gets to low,
some fertilizers are based on the idea of providing lots, ... possibly more than your plants could use, and so you must preform water changes to prevent things from building up to toxic levels

after this, i don't have clear reasons for or against regular maintenance as any reason could be contradicted by the next.

if i do regular maintenance on my one tank i won't learn what could go wrong, it won't inspire me to seek answers because i will never know what is going wrong to know what to search for

this also has drawn some criticism,
 
#14 ·
Substrate

is it possible to solve issues between anoxic zones in the substrate and roots adding O2 to the substrate ?

a DSB allows for Anoxic substrate.
needed for processing nutrient cycles
-i don't have a full list of each nutrient, but enough to know without any anoxic area, various nutrients will build up in forms nothing can use.

roots add oxygen into the substrate (for the health of the root)

are plant roots an enemy in this ?, or is there anything that can be done that would ensure that over time there will be anoxic areas that will remain to finish cycling these nutrients ?
 
#17 ·
You would need to make the substrate deep enough that plants would not root all the way down, or have significantly large unplanted areas to try and encourage anoxic zones but that wouldn't be a guaranty especially with heavily rooting plants. Also minimal to no current. Then you have to realize these conditions will have on more then just anoxic zones.

You are still lingering on nutrient cycling and redox which is again just the beginning of how an ecosystem operates. You fix the anoxic issue then there will be another issue and so fourth and so on. Issues that will have nothing to do with nutrient cycling and all about biological stability and viability.

Mulm build up and nutrients falling out of cycle is natural. Cycles are not indefinite, nutrients are always being added or removed to the system both organically and inorganically. You can keep asking and looking for ways around this but it is what it is. There is no current magic that lets you break physics yet and give you something for nothing.

I am all about pushing limitations and currently do and have for many years. The more natural you want to go the more the tank is going to look like it belongs in a swamp. Then when you get to the point where you don't even want to stick your siphon in there let alone your hand, you will then question why you bother pushing such limitations. Sure fish seem happy, plants look like crap from build up of mulm, any optional powerhead is probably clogged by mulm now too regardless of it if has any 'filtering' abilities. By then you have seen so many population explosions of things you have no clue of so you just let them be and wait for them to crash before touching the tank any further. I have lots of pictures of lots of things you generally don't want your tank to look much like both from the past and the present.

So yeah just change water, its much easier and rewarding IMO. You can do anything along with, soil substrates, non-filtered, ect and still be good.
 
#18 ·
Mikaila

you have no idea how thankful i am of your advice
i'm thankful i'm stubborn, or i would have given up

the redox and nutrient thing may be the basics, ... have to start somewhere (i'm guessing 5"), ... yes, it's got issues that i can't imagine how to overcome, aside from floating plants, not quite what i would prefer, ... and floating plants are only floating till their roots find ground, then they become anchored :(

ya, that's an area i don't have a fix or idea for.
 
#19 ·
Honestly, I think it would be an eyesore to have 5 inches of substrate in the tank.
 
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#20 ·
some plants are strict floating plants, other are considered rootless. Duckweed, dwarf water lettuce, hornwort, then the mosses are not considered rooting plants, roots primarily provide attachment are and very short.Anchored is diff then rooted. Most all stem plants have minimal roots that primarily anchor.

On the other hand an amazon swords roots can easily cover a 2x2' area.

Far as pore size I would say smaller, many plants root better in fine gravel then sand... but not always. Fine gravel to straight up topsoil my tanks still get good root development against the bottom glass with 3" of substrate.
 
#21 ·
mikaila,

i've got ideas on ensuring the life is going round and round, ... doesn't mean it will run stable, only that i've got ideas, including ideas that could naturally keep things in check (well 2 ideas for one situation)

i think over time as i look at things i may find a half-way point between this pursuit of self-sustaining and mechanical intervention, ... for now, while i'm running things around in my head, ... if i can do it in the aquarium, naturally, without need for me to get/use/install equipment, great this is what i will do.

if i can get it far enough that the only inputs i'm giving is energy sources, by all means i'm all for that long before i even begin, and this would be the optimal goal.

if i give up because of looks, then i'm a hypocrite
 
#22 ·
Mikaila, ...

you mentioned you think the tank (if i solve the nutrient cycle thing) would take on more of a swamp-like appearance.

this is going to sound so totally braindead on my part, ... what would that look like ?

in my imgaination i think of an overgrown area with plants and trees growing out of the water, heavily planted, duckweed, greenwater, ... but can't really picture more than that.

would that be about right, or is there other stuff you are thinking would happen ?
 
#23 ·
Mikaila, ...

you mentioned you think the tank (if i solve the nutrient cycle thing) would take on more of a swamp-like appearance.

this is going to sound so totally braindead on my part, ... what would that look like ?

in my imgaination i think of an overgrown area with plants and trees growing out of the water, heavily planted, duckweed, greenwater, ... but can't really picture more than that.

would that be about right, or is there other stuff you are thinking would happen ?
I' have a neighbor that asked for my assistance with their fish tank while they were admiring my ornamental pond.... their 10 gallon planted "guppy tank" was( is) the classic swamp.... I needed a mag light to look through the algae covered glass... dead and dyeing plants abound.. some sticking out of the tank.. I've seen septic systems that were cleaner... the woman told me the water hadn''t been changed in over a year.. they add water when the water level gets below the rim... did I mention the white crud covering the frame of the tank and light fixture...the guppies were alive .. so I guess that it is a self sustaining tank....I told her unless she was willing to follow a schedule i set up that I wanted no part in the "rescue".. she seemed to think that weekly water changes are unnessesary and troublesome... in the end she said she was just going to scrape the glass.. I wished her well and went home.... and stared at my tank(s) for an hour... enjoying the crystal clear water and active multispecies fish... IMHO, a bucket or two of water once a week is a small sacrfice for the enjoyment i recieve at watching my tanks...water chemistry is a complex thing... and for it to be the optimal home for our pets IMHO, we need to do the best for them we can.... and that includes removing nitrates, and replacing lost buffers and mminerals by doing regular water changes...
 
#24 · (Edited)
so ...
-things in the tank to deal with greenwater being too thick
-ensuring enough potassium for greenspot algae (and ensuring sufficienty other nutrients present to ensure there are no nutrient deficiencies
-plants that are edible and preferable to fish & critters pleasant.
-snails to deal with detritus in all it's forms

anything i missed or would that have solved every issue you saw ?

Edit:
i would never do this with a 10gallon tank, way too small

preferences, even for first attempt i would not recommend smaller than a 40 gallon

for arbitrary tank sizes, ... i've thought (as for round tanks) 1' diameter for each inch the species is long (this is worse than the gallon per inch rule of thumb, but gotta start somewhere)
 
#25 ·
there must be some limit to all growth to maintain stability. not sure when you intend to have all nutrients, well apart from carbon non-limiting constantly.

plants and algae occupy the same niche and directly compete. They both cannot be happy, you will lose plants typically in this situation. Or with happy plants they can produce compounds that work to inhibit algae. Typically greenwater should not be dense enough to be noticable, naturally this favors low O2 levels in the water column.

you have no understanding of mulm, detritus build up. Same with biofilms. I can post some horror pics of my tanks later.
Posted via Mobile Device
 
#26 · (Edited)
Flear,

OldFishLady had the closest example to self-sustaining tanks that I know of. (I'm not saying that other people don't. It's just that I read her posts about her tanks.) She isn't active on BF/TFK anymore, but you may want to read her threads about it.

Her tanks were heavily planted, and did not require frequent water changes. (But she did do occasional ones. In some of her posts, she discusses the frequency/infrequency of them.) The threads/posts I've seen were all on Bettafish.com, so you may want to look there. Also, it's worth looking at the photos in her albums (if they're still there). That may help you see what plants she had success with. Even though she's not active on the forum anymore, you may want to try PMing her to discuss this, if there's something you want to know more about. (Assuming she still has the option turned on to receive emails when a PM is sent.)

As for the ammonium/ammonia discussion, I just posted the following on Bettafish.com:
Ammonia test kits often don't distinguish between NH3 and NH4+. They just give you a "total" reading. Therefore, if your API test kit turns light green, it only tells you that the combined NH3/NH4+ reading is approximately 0.25ppm. But it doesn't tell you how much of each is present.....

We know that at a higher pH, there is more NH3 present (bad), and at lower pH, there is a shift towards a higher amount of NH4+ (less toxic). So below is an estimate of the relative percentages of NH3 at different pH values.

At a water temp of 25C (77F):
pH 6.0: Approximately 0.056% of Total Ammonia is in the form of NH3.
pH 7.0: Approximately 0.56% of Total Ammonia is in the form of NH3.
pH 8.0: Approximately 5.6% of Total Ammonia is in the form of NH3.


To determine how much NH3 is present, multiply the above % by the reading on your test kit. For example: Your test kit turns light green (0.25 ppm).
If your pH is 7.0: 0.25ppm x (0.56/100) = 0.0014ppm NH3.
At pH 6.0: 0.25ppm x (0.056/100) = 0.00014ppm NH3.

Assuming that the nitrifying bacteria require NH3 to grow, then it makes sense to me that the lower levels of NH3 (which occurs at the lower pH) will slow down their growth (and stall your cycle). They simply aren't getting enough "food."

(Please note: These numbers are estimates, and assumes that ONLY pH is the only factor in the equilibrium shift between NH3 and NH4+..... But this will at least give you an idea of the relative concentrations in your tank.)

Note: The above was for those who scored a low value in Jaysee's poll. :) For those of you who selected a 10, read on. (Insert evil laughter here.)

I used the Henderson-Hasselbalch equation to determine the relative ratio of NH3 to NH4+ at different pH values: pH = pKa + log ([NH3]/[NH4+])

In the above equation, Ka is called the acid dissociation constant. All acidic substance, including NH4+, have these values. It's a measure of the extent to which the acidic NH4+ dissociates in water to become the basic NH3. The values are easiest to find for "room temp" which is considered to be 25C (77F). At this temperature, the pKa for NH4+ is 9.25.

Now on to the math: (Are you still rating yourself a 10 on Jaysee's poll?)

If your pH is 6.0:
pH = pKa + log ([NH3]/[NH4+])
6.00 = 9.25 + log ([NH3]/[NH4+])
The ratio of [NH3] to [NH4+] = 0.00056
Multiply by 100 to turn this into a percent.....
So 0.056% of the Total Ammonia reading on your test kit is due to the presence of NH3.

If your pH is 7.0:
pH = pKa + log ([NH3]/[NH4+])
7.00 = 9.25 + log ([NH3]/[NH4+])
The ratio of [NH3] to [NH4+] = 0.0056
So 0.56% of the Total Ammonia reading on your test kit is due to the presence of NH3.

If your pH is 8.0:
pH = pKa + log ([NH3]/[NH4+])
8.00 = 9.25 + log ([NH3]/[NH4+])
The ratio of [NH3] to [NH4+] = 0.0056
So 5.6% of the Total Ammonia reading on your test kit is due to the presence of NH3.

The above is in line with the pH scale, which is a logarithmic scale. Each increase/decrease of one unit is a ten-fold increase/decrease in the concentration of H+ ions. (H+ ions are what makes a substance acidic. More H+ ions = more acidity = lower pH.)

:)
 
#28 ·
Well would be interesting to hear your opinions on those. I personally run as natural tanks as I can BUT I normally push those tank for high productivity. You want a biologically self sustaining aquarium, I personally go for the monetary self sustaining aquarium. Means low budget, DIY, and low upkeep too. Production is high and thus tank covers its own costs with output. But regardless i have set up tanks to push boundaries just to see what would happen. I can say the first year of 'neglecting'(or testing the sustainability) a tank is the easiest. It will be the microfauna and microflora that will cause issue. Some are transient boom and bust cycles which are typically in a unbalanced system. You can certainly achieve balance, maintaining it tho is a whole another thing.

Most my productivity tanks are soil tanks. I use topsoil mainly almost always with some additives then usually a sand cap on top of 1-3". I do have a bare soil tank running currently tho that has a substrate of just 2.5" of mineral enriched topsoil. I'm quite picky about my topsoil too. I've used both store bought and hand shoveled topsoil, the first is always more questionable IMO. Below are some of my sustainability tanks not driven for high production and more for simply seeing what happens.



Biofilms are yummy and they happen typically when you have unfiltered tank that is unmaintained biofilms come and go due to specific nutrient availability and such. Typically start as the 'oil film' on the surface if you have little to no surface movement they can get impressive. Surface movement mechanically breaks them down but most microorganisms don't like much movement, let alone filtration. Typically a biofilm like that lasts awhile, normally fish are fine, and normally I don't touch my 'whatever' tanks when they do this. They can stick around for a long time eventually zooplankton catch up and there is a swift boom and bust cycle, population explosions and collapses happen very fast when you simply let it run its coarse. That biofilm pictured above was around for a couple months then collapsed in about 48 hours do to a zooplankton boom. Then the zooplankton collapsed shortly afterwards. I've had this happen in multiple tanks multiple times.

Detritus and mulm become an issue eventually. Either stagnant or circulating tanks I have had this be an issue. Snails and shirmp make it worse IMO by adding to it. Without them you still have natural biological fallout from nutrient cycling. Bacteria, phytoplankton and zooplankton all naturally die in relatively short lifespans. This is the main source of mulm IMO in this kinda setup.


This is a previous filterless soil-based tank that did have circulation. After over two years some biological change caused excessive mulm build up and eventually I tore it down and redid the tank/substrate.

This is a current running tank. It is my bare- soil tank and it is stagnant. Mulm build up and such no shrimp and very few snails. Currently the rate up build up is slow enough no to be a concern.

Difficult pic to decipher. This is the same tank as the previous pic. What this is, is a localized nutrient deficiency. Again stagnant water and relying on diffusion is limiting even with 2.5" of topsoil its not a fool proof way to ensure nutrients. And localized deficiencies are naturally common. In this tank a large mass of bladderwort grows directly under the lights and has been having a major party with some cyanobacteria lately. Both are very good and happy with nitrogen deficient conditions. Being on the surface directly under the lights means they have the highest energy input zone which drives nutrient uptake and suddenly your lacking nutrients there. The duckweed in this tank also barely manages. Meanwhile the anubias and ferns beneath have no such issues with nitrogen.

I've never really had any of my long term 'neglected' tanks maintain macro/vertebrate life long term. Especially adult fish or fry. But again limits, typically the water column is nutrient devoid. If nutrients are available something will try to use them. Then competition, and whatever is most efficient usually pushes out its competitors either temporarily or long term. The chemical/nutrient cycles are a step in understanding the biological cycles. The biocycles effectively drive the nutrient cycles.

In comparison to my maintained tanks which are initially not that different then my unmaintained tanks I find my unmaintained tanks meh, which in a way perpetuates their being unmaintained. Some are both soil tanks with same basic setup and in the end differences that leads to super happy and crazy plants and excessively stocked happy fish is simply maintaining them and changing water. And by maintained I mean I had to spend 3 whole minutes of my life laying on my couch tonight watching one of my high productive tanks finish filling to the trim for is 50% weeklyish change. But I do understand we all find different things rewarding.
 
#32 ·
Guppies and all :)
 
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