Bioactive aquariums?

[OnlyGenusCaps]

I'm tearing down and sterilizing a 75 gallon right now that had a total fish loss situation.  As I was doing that, I noticed something interesting.  Despite the fact I only used river rock, gravel, and play sand as the substrate, I had dirt.  Like humus soil! 

Here is a shot of it while I was cleaning it out and noticed it:

And here is one that's a bit clearer after I drained the tank:

As you can see, this is no small amount of organic soil in the tank.  The only thing that could have been a source is the Malaysian driftwood I had in there.  As I mentioned, all of the fish died in this tank.  After that I turned off the light and left the tank for about a month to let any decomposition finish.  In that time the other life in the tank took off!  The driftwood in particular was coated with isopods and there were amphipods swimming like krill in the ocean, in swarms.  These two I put in there as a live food source.  I also had piled of ramshorn snails in there, which I have in no other tanks and I still don't know how they got in there.

So, what could have created this soil?  Well, the ramshorns, as mystical as their appearance was, don't seem like likely candidates as they live in many aquaria and don't do this.  I'm thinking that either the amphipods or isopods, or a combination of the two, were able to degrade the driftwood to this extent in a little over a month!  Certainly the driftwood was coated with the isopods when I took the pieces out.

I know some people do Walstad and/or dirted tanks around here.  I'm curious if any of you have noticed a process like this happening this quickly?  Also, do you put in isopods and amphipods?  "Bioactive" terrariums which include clean-up crews such as collembola and isopods that act as a snack for the focal species are all the rage now.  Does anyone know of "bioactive" aquarium keepers like this?  I'm curious, because if I ever keep a dirted tank, I think given the results here, I would absolutely add these little critters.  I also feel like this entire area of discussion is right up @Streetwise's alley. 

[Streetwise]

I grew up in the woods. What feeds the soil? Dead wood, and yearly leaves, which also change the chemistry. Add in animal waste, plus sun, water, insects, invertebrates, fungi, bacteria, algae, etc.

@OnlyGenusCaps, maybe you can keep this substrate going, or save some for smaller containers.

(Keep wood in your tanks!)

[lefty o]

decaying matter, plants, wood, fish poop, all become dirt/soil.

[OnlyGenusCaps]

On 1/12/2022 at 9:17 PM, Streetwise said:

maybe you can keep this substrate going

No.  Too high a risk this unknown cause of fish loss is still in there.  Everything is getting tossed and the tank will get a first run of alcohol, then 12% peroxide. 

On 1/12/2022 at 9:17 PM, Streetwise said:

Dead wood, and yearly leaves

On 1/12/2022 at 9:31 PM, lefty o said:

decaying matter, plants, wood, fish poop, all become dirt/soil.

And yes, I realize that rotting organic material adds to soil.  My surprise is the rate of disintegration of the Malaysian driftwood.  I've had this wood in tanks before, but never seen this sort of degradation at anywhere near this speed.  I find the speed of the process to be the interesting component in this case, not the occurrence itself. 

I was thinking for those who do more ecosystem based tanks, that this might be of interest.  I do not run any of those currently, so perhaps I have misjudged that.  I was thinking that the process would be useful in an aquarium, but perhaps it would be detrimental if the rate of wood loss is so high?  In any case, the fish would have kept the numbers of the carious critters in check and reduced the wood loss, but this process would still be going on in the background.