9 replies to this topic

[junebug]

Hello all!  I am (still) in the planning phase of my sunfish tank, and a question came up.  Given this is a native tank, and given I live in the US and can get the plants/substrate/whatever I need fairly easily, I want to make this tank as natural as possible.  My tropical tanks are all Walstad method, heavily planted breeding tanks (with the exception of the bettas) and it occurred to me I'd really like to take things one step further.

This involves in my opinion the introduction of a Deep Sand Bed to my tank.  If I do this, I plan a thin base layer of soil topped with the sand bed.  The sand bed is meant to act as the main biofilter in the tank, and work for denitrification as well.  I want a thick, stable anaerobic bed beneath the top layer.

Has anyone here ever done this?  It's meant to replicate the natural environment of a slow moving stream or possibly a swamp.  That is, in it's application in freshwater.  If anyone can offer advice on setting one up appropriately I'd very much appreciate it.  I plan to plant the tank with rooted plants, stock it with ghost shrimp, scuds, and blackworms *before* adding fish, so that should take care of aeration in the top layer of the soil.  

 

I've been chatting with a friend who works in a water treatment plant.  I know very little about water treatment for human consumption, which is what it seems he does for a living, but apparently there is a huge "pond" before the water reaches the mechanical plant, in which the suspended dirt is meant to collect at the bottom.  He informs me that this is where collection of bacterial samples occurs, and when working in the pond, the anaerobic zone occurs at 4" deep or more.  This is based on the presence of the black "muck" that becomes crude oil, the scent, and the depth at which his boots get stuck in the muck.  Does this sound right?  4-6" of sand?  Would that be deep enough to keep the blackworms out of the intended anaerobic zone?  

 

And probably the most important question: What are the warning signs of a problem? I realize I shouldn't be able to smell the anaerobic bacteria in a tank set up like this.  If I can, immediate removal of the fish and inverts will be my first step.  Are there other signs that there is a problem?  How do I know if I've managed to culture the right sort of denitrifying bacteria in the anaerobic zones?  The last thing I want is something that can harm the fish, and I know many anaerobes carry that risk (mycobacterium immediately comes to mind)

Any help on this would be much appreciated.

[Matt DeLaVega]

I think if you search for threads by farmertodd and Erica Weiser you may get so good info.

[Evan P]

I run mostly deep sand beds, at least whenever I can, and they are great. I think you have the right idea of going with an inch or so of soil followed by 3-5 inches of sand. This formula has worked out very well in my experience. Honestly, I think the "dangers" are more urban legend and paranoia than anything else. Really, it's not worth worrying about.

[Sean Phillips]

I have a 4" deep sand bed (with one handful of gravel mixed in) in one of my 20 highs (24"x12"x16"). It looks very nice and allows the blackworms in the tank to colonize and reproduce quickly, which gives the inhabitants food to graze on all day. Just be warned, do not put it in direct sunlight, mine unfortunately is which makes algae grow INCREDIBLY fast being that there's no plants in the tank.

[gerald]

A sand bed in a fish tank will be much more nutrient-rich and will get anaerobic much closer to the sediment surface than in the raw water settling pond at a water treatment plant, which usually has very low nutrient input.  I dont see any reason that a deep sand bed would increase the risk of Mycobacterium -- it grows mainly in aerobic areas, especially on the tank walls at the water surface where oils and food residue accumulate.   IMO plants are a more reliable way to remove nitrate than anaerobic denitrification, which requires a narrow range of conditions.

[Michael Wolfe]

I agree with Yeahson on this... Deep substrate is the way to go.  The only issue you will have is you start off by saying "sunfish" in the first line of your post... that will be a problem... on day, eventually, someone will decide that they have to have a pit... then you are going to have a mess.  Deep sand/soil substrates are great.  I am looking at three inches of red Georgia clay and a few swamp darters, bluespotted sunfish (these are Enneacanthus... not Lepomis) and more val that I thought possible.  So do it... but leave the Lepomis for a different setup.

[junebug]

Why would a DSB be an issue with lepomis?  It's actually going to be a mixed sunfish tank, with northern longears, dollars, and a smaller enneacanthus spp.  Not sure which though.  

I know they dig, that's why I was planning on a very deep bed, particularly since a 3" bed isn't going to have any more value than a normal depth sand bed.  5-6" seems deep enough that the anaerobic layer would be below where they'd dig to.  Of course if it's going to be an issue, I can always run it in the sump instead of the display.  

 

Gerald, I guess what I'm asking is how to cultivate the right conditions for denitrifying bacteria to grow along with the aerobic, nitrifying bacteria.  The tank will also be planted, I'm not worried about that.  

[Michael Wolfe]

I have a warmouth who has successfully and repeatedly wallowed out a spot in his tank all the way to the glass.  I'm not saying the tank will crash or anything, just that it may not look pretty unless yo like the dirt scattered about... with red clay it settles out pretty well and I don't mind it, but it is not a nice planted tank look, it is a natural look.

[littlen]

To reiterate Michael's point, the sunfish (typically a mature male) will clear nesting sites and disturb your anaerobic layer of sand/soil.  Depending on the conditions, this could release a lot of hydrogen sulfide into the tank and cause further issues.  But a large tank, with a little disruption shouldn't be a problem if it is off-gassed by filtration/aeration.

To answer you other questions, the blackworms will keep themselves from entering into the anaerobic layer.  When you see them with their heads poking out of the sand, wafting around, they are breathing.  They require oxygenated water to survive so they won't spend any time in an established anaerobic layer mucking around.  (Sorry for the pun).  Adding something like MTS would certainly mess up what you're going for as they will burrow down deep into substrates.

You'll know exactly when and where your anaerobic bed starts.  You should see a distinct, darkening layer on the glass an inch or so below the surface of the sand.  Furthermore, you'll notice gas bubbles forming deep in the sand [the hydrogen sulfide I mentioned].  

[junebug]

Thank you so much for all the help, guys  It looks like this might be a better fit for my shiner tank than the sunfish tank LOL.  So I might do that, along with a small DSB in the sunfish's sump.  That will require a slight modification to the sump setup, but I think I can manage it