Freshwater Deep Sand Bed (DSB)

Anoxia

Anoxia

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Jan 12, 2010
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I am trying a deep sand bed in my 29. I have no idea if it will work or not, as I seem to be doing everything backwards, but I'll let you know either way. All are welcome to give me advice or criticism, or whatever.

I left most of the eight-year-old dirty gravel underneath, put one inch of red clay mixed with topsoil over it (so mud, basically), then topped that with some more of the dirty gravel, then put about an inch and a half of playsand over that, with a little sprinkle of dirty gravel on top just to theoretically help break up any surface compaction. Total depth is about four and a half inches.

This is my first planted tank, and it is still cycling. I am doing small frequent water changes three or four times a day, trying to keep the fish and plants alive through the cycle. Like I said, I've done a lot of it backwards. Hopefully this won't last long, and I will be able to add worms and snails soon. I'll post pictures eventually, once the higgeldy-piggeldy slows down some.
 
Welcome to AC! Start a thread on it if you like..sounds interesting!
 
Thanks! I got my blackworms and Malaysian trumpet snails, and added more live plants, improved my lighting (from .5 watts per gallon to 3 WPG), and I am putting my DIY CO2 thingy together tonight. Still changing 25% of the water 4 times a day, though. I'd like to be done with the nitrogen cycle fairly soon, but I won't let my fish get ammonia poisoning, either.
 
It sounds like you've got a neat plan! Welcome to AC
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Anoxia said:
I left most of the eight-year-old dirty gravel underneath, put one inch of red clay mixed with topsoil over it (so mud, basically), then topped that with some more of the dirty gravel, then put about an inch and a half of playsand over that, with a little sprinkle of dirty gravel on top just to theoretically help break up any surface compaction. Total depth is about four and a half inches.
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Interesting: The old gravel underneath may serve as a sort of plenum. Hopefully, that will do more good than harm; plenums are out of vogue, as they definitely aren't necessary, may actually reduce the effectiveness of a deep sand bed.

Why dirty gravel? The bacteria/organisms in it will all quickly die in the anoxic layer, so this serves no "quick start" function.

This is my first planted tank, and it is still cycling. I am doing small frequent water changes three or four times a day, trying to keep the fish and plants alive through the cycle.
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Assuming you mean that your nitrites/ammonia are spiking, that is probably because of the gravel you left at the bottom, above. It was full not just of nutrients, but of living organisms that are now dying and rotting, while the anoxic component is not yet functional.

Had you done it without the dirty gravel on the bottom, it probably would have been a lot more stable at the outset. You could certainly have used the gravel to "seed" the upper layer, though.

I am interested in how this turns out for you, in the long run, as I'm planning to try something similar.

Oh, note that freshwater fish can handle, even prosper in, much higher nitrates than are widely accepted in the Conventional Wisdom of Aquaria world. Aquaria is, in general, rife with what amount to old wive's tales accepted as fact. So if it's a nitrate spike, not a nitrite spike, that is causing your cycle-disruptingly rapid water changes, then it may not be so necessary.

Do remember that water changes are a mixed blessing. One reason to have a deep sand bed is that you can avoid doing changes. Water changes stress both the tank's biology, and the fish.
 
Thank you, kazvorpal, for your thoughtful advice. I had some similar doubts in retrospect about my decision to leave the old gravel underneath, but it doesn't seem to have done any harm thus far - time will tell. I certainly don't think it was a wise move on my part, nor I would recommend it to others, when pure sand apparently works just fine. I have noticed, a couple weeks into this experiment, that the clay/sand that is closest to the gravel is turning black first, probably aided by the decaying organisms you mentioned.

Ammonia and nitrates are now at zero, and I have a barely detectable nitrate level, so I have stopped the water changes, and I am just going to test it daily for a while, to see what happens. There are bubbles coming up on occasion, which seem to have no affect at all on the fish or plants.

I added a second batch of blackworms today, to replace my initial supply, which disappeared, presumably eaten, and I may need to add more livebearing snails, too. Fish behavior is normal, though they still haven't regained their former interest in flake food. They are nice and fat, so I guess they just prefer blackworms, and I won't worry too much.

I hope you will share your FWDSB project online, not much seems to have been written on the subject yet. The pioneer aspect is kind of exciting!
 
Oh, I never did set up that DIY CO2 unit, I decided to just watch the plants, and see if I think the CO2 is really needed or not. So far, it doesn't look like I'll need it.
 
Anoxia said:
Oh, I never did set up that DIY CO2 unit, I decided to just watch the plants, and see if I think the CO2 is really needed or not. So far, it doesn't look like I'll need it.
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I can't imagine many circumstances in which you'd need a CO2 unit. Water naturally absorbs CO2, and naturally expels O2...that is how the ocean keeps the ratio of O2/CO2 in the atmosphere stable.

Which it does, despite global warming profiteers' implications to the contrary.
 
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