20g long new Walstad tank, advice on bioload, plant density, and filtration

[quo usque]

I set up a 20g long Walstad tank 2 days ago. I have a heater, but no filter. It is divided in half because it houses betta fish.

Setup:
1.5 inches organic potting soil
.5 inches gravel (~3mm-6mm size)

lights:
crappy LED that came with the tank hood
13 watt florescent desk lamp (6500 k)
1 incandescent desk lamp, which I plan to switch out for another florescent as soon as I drag myself to the hardware store. I'm aiming for ~1.5 watts per gallon, not counting the LED.

plants:
2 amazon swords
2 java fern
2 lace java fern
2 potted dwarf sagittaria
several non-potted dwarf sagittaria
2 cryptocoryne wendtii
4 purple cabomba
2 ambulia
and an ungodly amount of hornwort. Before I put it all in the pile was the size of like 2 guinea pigs.

Setup went pretty well. The water was butty at first, but it has cleared up since. There is still a bit of dirt floating on the top, but I've been skimming it off and it's mostly gone. the tank seems to have fully cycled in 2 days- ammonia spike, then nitrite spike, now both are zero. Nitrates are also zero, I'm assuming because the plants are taking them up. Ph is 7.8 and temperature is 80. I don't know the exact hardness of the water since I don't have a test kit for that, but since we have lime residue all over the faucets, I know it's reasonably hard.

I added the 2 betta fish this morning, and they both seem to be doing pretty well (although they were both confused as heck for a while, because their tank was completely bare before, lol)

I am planning on using the 5-4-5 siesta regimen of photoperiods recommended by Diana Walstad in her book. I am not planning on dosing the tank at all.

my questions:
Do I have too many plants for the amount of fish that I have? Do 2 bettas generate enough waste to support that many plants?

If they are not enough, can I make up the difference by feeding them extra food so that it will decompose and feed the plants? How much extra food?

Or, should I get some snails or shrimp or catfish, or something else that does ok with bettas (with 20g and lots of places to hide, I think maybe a group of like 6 tetras per side would do ok?)

I really do have a lot of hornwort in there. Is it possible that it will kill the plants beneath it by shading them? How do I know if I should remove some, and if so, how much?

I am expecting lots of fast plant growth (I hope so anyway, as the success of a walstad tank kinda depends on that...) so I know I'll need to trim. I don't want to trim too much and cause an ammonia spike. How do I know how much/often to trim my plants?

If I end up having to remove some hornwort, is there a way I can keep it alive in a separate container? Can I just stick some soil and water in a bucket with the hornwort and leave it in the sun?

Finally, about filtration, water flow, and oxygenation-

I currently have no filter (I've been sustaining these 2 fishies with annoyingly frequent water changes). Walstad recommends against a filter with bacteria as the bacteria competes with the plants. She also recommends against things like airstones and filters that pour water back into the aquarium, since the rapid surface agitation lets all the CO2 escape.

Walstad says she does just enough to provide the fish with the oxygen they need, but is vague about what exactly she uses to do that. She also says that some amount of water circulation is beneficial to the plants by spreading nutrients and preventing dead spots.

How should I oxygenate and circulate my water? I obviously can't have too high of a flow rate, because both the betta and the cabomba won't like that. Would I have to have a device for each side of the tank, since the holes in the divider really don't allow much water flow? The cheaper I can do this, the better. I am a broke college student.

Also, I'd like to add something to help aerate the soil. Snails? Worms?

I apologize for all of the questions- I have never kept fish before, and I wanted to do a Walstad tank because I can't even get my laundry done weekly and longterm weekly water changes would result in me forgetting to do them and killing the fish. I would have tried to stabilize the tank before getting the fish but they were a surprise adoption from a psych lab so they wouldn't get euthanized.

 

[Caliban07]

I set up a 20g long Walstad tank 2 days ago. I have a heater, but no filter. It is divided in half because it houses betta fish.



Setup:

1.5 inches organic potting soil

.5 inches gravel (~3mm-6mm size)



lights:

crappy LED that came with the tank hood

13 watt florescent desk lamp (6500 k)

1 incandescent desk lamp, which I plan to switch out for another florescent as soon as I drag myself to the hardware store. I'm aiming for ~1.5 watts per gallon, not counting the LED.



plants:

2 amazon swords

2 java fern

2 lace java fern

2 potted dwarf sagittaria

several non-potted dwarf sagittaria

2 cryptocoryne wendtii

4 purple cabomba

2 ambulia

and an ungodly amount of hornwort. Before I put it all in the pile was the size of like 2 guinea pigs.



Setup went pretty well. The water was butty at first, but it has cleared up since. There is still a bit of dirt floating on the top, but I've been skimming it off and it's mostly gone. the tank seems to have fully cycled in 2 days- ammonia spike, then nitrite spike, now both are zero. Nitrates are also zero, I'm assuming because the plants are taking them up. Ph is 7.8 and temperature is 80. I don't know the exact hardness of the water since I don't have a test kit for that, but since we have lime residue all over the faucets, I know it's reasonably hard.



I added the 2 betta fish this morning, and they both seem to be doing pretty well (although they were both confused as heck for a while, because their tank was completely bare before, lol)



I am planning on using the 5-4-5 siesta regimen of photoperiods recommended by Diana Walstad in her book. I am not planning on dosing the tank at all.



my questions:

Do I have too many plants for the amount of fish that I have? Do 2 bettas generate enough waste to support that many plants?



If they are not enough, can I make up the difference by feeding them extra food so that it will decompose and feed the plants? How much extra food?



Or, should I get some snails or shrimp or catfish, or something else that does ok with bettas (with 20g and lots of places to hide, I think maybe a group of like 6 tetras per side would do ok?)



I really do have a lot of hornwort in there. Is it possible that it will kill the plants beneath it by shading them? How do I know if I should remove some, and if so, how much?



I am expecting lots of fast plant growth (I hope so anyway, as the success of a walstad tank kinda depends on that...) so I know I'll need to trim. I don't want to trim too much and cause an ammonia spike. How do I know how much/often to trim my plants?



If I end up having to remove some hornwort, is there a way I can keep it alive in a separate container? Can I just stick some soil and water in a bucket with the hornwort and leave it in the sun?



Finally, about filtration, water flow, and oxygenation-



I currently have no filter (I've been sustaining these 2 fishies with annoyingly frequent water changes). Walstad recommends against a filter with bacteria as the bacteria competes with the plants. She also recommends against things like airstones and filters that pour water back into the aquarium, since the rapid surface agitation lets all the CO2 escape.



Walstad says she does just enough to provide the fish with the oxygen they need, but is vague about what exactly she uses to do that. She also says that some amount of water circulation is beneficial to the plants by spreading nutrients and preventing dead spots.



How should I oxygenate and circulate my water? I obviously can't have too high of a flow rate, because both the betta and the cabomba won't like that. Would I have to have a device for each side of the tank, since the holes in the divider really don't allow much water flow? The cheaper I can do this, the better. I am a broke college student.



Also, I'd like to add something to help aerate the soil. Snails? Worms?



I apologize for all of the questions- I have never kept fish before, and I wanted to do a Walstad tank because I can't even get my laundry done weekly and longterm weekly water changes would result in me forgetting to do them and killing the fish. I would have tried to stabilize the tank before getting the fish but they were a surprise adoption from a psych lab so they wouldn't get euthanized.

Check out my thread 'caliban's dirtied 46 gallon bowfront'

It should answer lots of your questions. I've had lots of experience with this approach and although I was extremely optimistic beforehand it didn't quite work out how I planned it.

Let me tell you that Walstad has recently changed her mind on oxygenation and even water changes and now believes low oxygen is the reason many report problems with the method.

You're going to have a problem with the bettas and flow in this tank because the really do not like much.

The breakdown of organics in the dirt requires lots of oxygen. Oxygen is not very soluble in water. It takes roughly 6 years for oxygen to travel from surface to a depth of 6 meters and nearly all oxygenation occurs by surface agitation in natural waters.

Luckily the Bettas can breathe from the atmosphere but low oxygen content in a dirtied tank can cause the substrate to become anaerobic. This is not good and will create lots of problems for you and your tank.

What's more, although carbon is much more soluble in water that oxygen, it still diffuses 10,000 times slower in water than it does in air. Carbon in a Walstad tank is generated by the bacterial breakdown of organics in the soil but guess what, the Bacteria cannot do this without oxygen. So the plants that have little carbon and little flow bringing it to then begin to photo-respire and actually contribute to the low oxygen levels. At night when plants are releasing co2 it can be enough to wipe out your tank. Then because you are doing no water changes and not disrupting the surface of the water, you get an oily biofilm that further restricts gas exchange and houses Nasty bacteria as well as good and bettas spend the majority of there time wallowing in this slick.

You have a nice shallow depth with your substrate but you're gonna want to get oxygen to diffuse in to the top layer of water then passed around the tank. If the plants are healthy they will add oxygen to the water.

The good thing about surface agitation is that it brings oxygen AND carbon dioxide to the water. The amount of carbon is minimal though. Probably about 0.6ppm indoors. But if you have good oxygen transport the soil will be producing carbon that will be beneficial to the plants before it outgasses. The other good thing about surface agitation is that it is constant and oxygen and co2 is constantly being replenished, so when the plants adapt to this level there will never be a shortage although some plants my not adapt to this most will. If you do the siesta you will get fluctuating levels or shortages of carbon dioxide which will confuse the plants as the have energy expending mechanisms in place to adapt the makeup depending on carbon availability. Plants need stability. At night surface agitation will also stop co2 levels rising and wiping out the tank.

Water changes are now also recommended but you may only need to do 20% once a week or 50% every two weeks. You just need to make sure the tank is healthy. Read through my thread to get an idea of the trails and tribulations of a dirtied Walstad approach.

The purple cabomba won't stay purple without good light and carbon. The other plants are fine for this setup. Soil has micronutrients in abundance but look out for macro deficiencies if you are changing water often.

Good luck.


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[Caliban07]

By the way in my opinion a soil substrate as far as the plants are concerned cannot be rivalled. For more information on why check out my other thread 'the soil substrate explained'


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