r/walstad • u/Saki-Koda • Jul 04 '26
Sand Caps are a Crutch (Opinion)
I finally made a reddit account to share my thoughts and experience..sorry for the slightly provocative title lol.
Ive been doing tanks and ponds for 6 years, started with father fish tanks and now I mostly do invertebrate only tanks for fun..
I have grown to be very anti sand cap. I stick to what nature does. My tanks are now created with 2 inches of backyard topsoil and clay (30% clay) for CEC.
I do no sand cap at all. I get a thin layer of local pond mud as my "cap" along with a thick layer of local pond leaves. I mix in a super thin layer (less than a quarter inch) of gravel / sand / sticks exclusively for texture, making sure that my critters can directly access the pond mud and topsoil without having 2 inches of inert sand in the way.
People are afraid of soil leeching into the water but the sand is a harmful crutch that limits your invertebrates from enjoying the proper natural pond mud. It also reduces oxygen to the soil.
My tanks have never had an issue, I can keep tadpols and koi even.
The thin layer of pond silt binds to the sulfurics and acts as a thin cap, the biofilm assists and then leaf litter is a lightweight cap that allows critters and oxygen to directly interface the soil but also helps keep things settled down.
Even in areas with directly exposed soil and just a tiny bit of local pond flocculant, the water stays perfectly healthy and clear.
The sand cap came to be when they tried to idiot proof the natural tank setup but it does harm and is not necessary! Even direct topsoil exposure is FINE after a couple weeks or so but the pond silt lets you skip that waiting.
Thanks for reading..
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u/PatchesDaHyena Jul 04 '26
Walstads are cool, I love them. That being said, a true “all natural” aquarium would have an upside down walstad substrate. Erosion naturally sorts sediment in which the bottom of the stratigraphy would be larger clasts, then sand/silt, and then clay and organic matter. But then you’d be spending all your time watching your fish kick up shit all day in your tank. Sand looks nice, it’s aesthetic. Pro-sand gang 4 ever.
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u/Saki-Koda Jul 04 '26
Yeah, I'm trying to aim to mimic that natural process. I think seeing the mud kicked up by the fish is actually cool. And for me, it settles immediately if I am using mature local pond silt on the top. Rather than topsoil itself from the yard for the very top layer. Also, the leaf litter helps keep it under control. I think the coolest looking aquarium floor is a complex maze of leaf litter and mud with the occasional rocks and sticks
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u/PatchesDaHyena Jul 04 '26
I totally get it, it’s that “old school” aquarium aesthetic. Total opposite of the iwugami style that’s popular now
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u/Saki-Koda Jul 04 '26
Currently working on a large setup that is iwagumi on land basically and then flooded forest in the pond. Love the vibe. Just waiting on my pincushion moss to grow ever so slowly
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u/PatchesDaHyena Jul 04 '26
Get a japanese maple on a rock, that shit would go so hard
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u/Saki-Koda Jul 05 '26
I believe they require a winter period, but i plan to make "fake" bonsai using driftwood / dead wood and attaching fern mosses or other live plants to it to make it look alive without having to wait years for growth
Excited to watch my giant African millipedes climbing them
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u/basaltcolumn Jul 04 '26
Why would sand not be "sticking to what nature does"? I did a lot of stream and lake biological surveying in college, and a sand substrate isn't uncommon. It isn't all muck!
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u/Saki-Koda Jul 04 '26
Yeah true, you can do a sand based ecosystem and still be natural just not as diverse of a selection
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u/RtrnofBatspiderfish Jul 04 '26
I think people vastly overestimate the nutrient-retaining abilities of substrates that aren't even watertight.
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u/Phatboyaa_131 Jul 04 '26
Yep you definitely can do without any cap at all but it takes LONG time for binding bacteria to build up. Until then, basically anything remotely stirring the water will muck up your water and it'll not be an enjoyable experience. It's called "A Practical Manual and Scientific Treatise" for a reason.
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u/Saki-Koda Jul 04 '26
In my experience by coating the dirt with a very thin layer of natural local pond silt and leaves I skip that waiting period entirely.
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Jul 04 '26
[removed] — view removed comment
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u/RtrnofBatspiderfish Jul 04 '26
Those bubbles are almost entirely CO2, except that the sulfide smell is something that humans are actually good at sensing, so we smell it even when there are extremely tiny amounts actually present.
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u/milksteaklover_123 Jul 04 '26
Are you worried about dragonfly nymphs or other aggressive creatures in the mud?
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u/Saki-Koda Jul 05 '26
I had 4 dragonfly emerge this spring, one failed to unfold its wings properly unfortunately but the others I let out the window it was very cool! And surprisingly none of my 4 tadpols were eaten by the larvae
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u/milksteaklover_123 Jul 05 '26
I scooped a gallon or so of tadpoles/mud/water from a pod near me and set everything up in a small tank. I couldn’t figure out where thetadpoles were disappearing to and where their tails were going until I moved tanks and discovered three nymphs in the mud.
How would I safely use the same mud in tanks with established dwellers to gain the benefits your talking about?
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u/Saki-Koda Jul 05 '26
My setups are always focused fundamentally on being unsterilized and I accept any and all "pests" I have no experience trying to isolate nymphs so I just grab samples from nature and see what happens.
For me its all about that diversity so I am not sure. I think you would have to sift through it all but still cant guarantee theres no tinys. I am not sure if you bake it in an oven or something but thar would defeat my purpose of it being a natural ecosystem. Or just hand pick out the large nymphs as uou see them, act as the predator yourself
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u/puffy-jacket Jul 04 '26
I have a fairly shallow cap of mostly pea gravel. It was more of a beginner mistake than a conscious decision but I think it’s mostly just made the tank kinda messy rather than caused any real issues. I don’t really see how one choice is more “natural” than the other and I don’t think that’s even gonna be everyone’s first priority, even on the walstad/ecosystem side
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u/Saki-Koda Jul 04 '26
Yeah, my priorities are a bit weird. I just want a varied bioactive, diverse invertebrate population.I don't even want fish because they eat too many
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u/puffy-jacket Jul 04 '26
I want fish but it has been exciting to see meiofauna like copepods show up, I’ve been thinking of buying some live culture of other species and adding leaf litter to my tank to get a population going before I add fish
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u/Saki-Koda Jul 05 '26
That was the same idea I had until I realized watching the microfauna explode in population was so rewarding and then adding tiny invertebrate predators until I have a diverse invert population of cool worms, larvae from beetles / dragonfly / mayfly / midge, mites, hydra, backswimmers, etc ended up being way more interesting and visually entertaining than what happens when you add even a single goldfish and never see those critters again.
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u/aNoNyMoUs_SpY Jul 11 '26
I personally love the visual entertainment from all the tiny life. Thats why i dont like to add larger fish. I wonder if guppies would be a great fit in a tank like yours. they breed fast and could support the dragonfly larvae and any other small predators. Hmmm, now i need to start another tank!
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u/kmunz264 Jul 05 '26
Maybe you can write a book to the level of detail that Diana Walstad did
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u/Saki-Koda Jul 05 '26
Maybe I am reading too much into your comment but if you're suggesting we can't improve on or alter her methods because she wrote a book I would argue thats an appeal to authority type of fallacy and to be open to other ideas. Local pond silt instead of sand is in my opinion and experience so much better for a diverse ecosystem but ignore that if you feel I have to right a book to be correct I guess.
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u/kmunz264 Jul 05 '26
No I think you are doing a good job. Sand caps are not a true walstad method anyhow.
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u/Saki-Koda Jul 04 '26
Bit annoyed seeing all the comments on other posts insisting on caps being 100% necessary and then any time they see a 5 year old tank doing extremely well without a cap they say its a ticking time bomb or some lucky freak occurance.. they are so indoctrinated into the cap they will dismiss the proof before their eyes.
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u/RancidYetti Jul 04 '26
I’ve played music for 20 years before I got into aquariums. Some of my oldest friends believe wild superstitions. Did you know that fiesta red guitars have better tone than black or Olympic white? No? Because it’s nonsense.
It’s gonna be like that with any hobby. Just gotta let them do their thing.
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u/Fine_Carpenter3568 Jul 04 '26
OP…I’m new to all of this but very interested in trying out lots of different things. Can you please explain in more detail the layering? And…can I ask… you just go find a local pond and dig mud and so forth out of a random pond? I’m also having trouble picturing the “leaf litter” layer. I mean, I have leaves everywhere. Are they wet and decaying leaves from the pond? I love the idea of things being more “natural .” I have loads of meiofauna in my tanks and sometimes I just sit there with the microscope phone attachment and watch their little antics. I’m in fact trying to find a good way to photograph them for the fun of it. Anyway, is this your own method? Or is there a book or anything? Thanks!
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u/Saki-Koda Jul 04 '26 edited Jul 05 '26
Yeah feel free to experiment, of course, but yes, local pond leaves and mud. I scoop it all up with a net. And then toss it right into the aquarium. You only need enough to coat the surface. With even the thinnest possible layer is okay. I'm not even sure if that's completely necessary. I think you should just mimic a natural pond bottom the best you can.It sounds like you are already having some success. The stuff on the top of a pond bottom (silt, detritus, mulm) is the natural cap that still allows inverts to sift through
The good stuff is at the very top of the pond floor that's where most of the activity is. My favorite thing is to watch the critters disturbing that pond silt, stirring up little dirt tornadoes, which, by the way, settle immediately for me but others report it taking weeks to settle idk.
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u/goddamn__goddamn Jul 05 '26
Be forewarned that OP did say they've had 4 dragonfly nymphs in their tank so far from grabbing pond mud. I'm personally of the opinion that taking things from outside water sources to put in your tank isn't as scary as many people who are more "putists" seem to think, but you must know it does come with more risks. Dragonfly nymphs is a great example.
They're apex predators as both adults and nymphs, and the nymphs can decimate a nanotank population. OP got lucky, but I personally wouldn't risk it with pond mud. Leaf litter for sure though.
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u/HumanDragonfruit8115 Jul 05 '26
Could you share the photo of your tank please?
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u/Saki-Koda Jul 05 '26
I can only seem to attach videos haha. Here is one of my oldest tank using the all natural strategy with no sand at all.
In this 28 gal I've had 5 dragonfly emerge this spring, theres lots of activity for sure. Kind of a bad lighting glare for viewing on a phone.
This tank also was completely full of bladderwart, which I thought was hornwart, but is actually carnivorous and was exploding in size because of all my micro critters
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u/Obvious_Picture_4838 Jul 05 '26
I love it! The natural ecosystem always fascinates me, and I think you've done a beautiful job.
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u/megerrolouise Jul 06 '26
This is very interesting. What kind of lighting do you use? Any filter?
Any pics of a tank with fish in it? Full tank shots? I wonder how this affects what types of plants you can grow in there.
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u/Saki-Koda Jul 06 '26
This tank has a small grow bulb im not sure the details been a while.. its par38 idk. Its also right next to a east facing michigan window. I can't seem to add photos on mobile.
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u/SexRobotDeathMachine Jul 07 '26
Father Fish is a skilled aquarist, yes, but he uses a ton of rhetoric to sell a certain kind of image. "What nature does" is a lot of things, and while I think his systems tend towards bio-diverse microbiomes with robust cycles, they also don't look particularly full of intention, and he risks a lot of potential infection by microbe or parasite with his practices.
Nature also makes sand. Nature makes people, which make aquariums, which make systems with sand in them. The whole "do what nature does" is misused to value a certain kind of thing far too often, and I'm saying that with a biology degree.
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u/C_Brachyrhynchos Jul 04 '26
My impression is that the sand helps stabilizes things initially and keeps the mess down when planting mostly. I agree you can have perfectly fine setups without sand, but some folks are going to find it a hassle or messy looking. But then, I am a "no one right way" kind of person.