Keeping dirt nutrient rich with overfeeding questions? - The Planted Tank Forum
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post #1 of 8 (permalink) Old 03-18-2013, 10:02 AM Thread Starter
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Keeping dirt nutrient rich with overfeeding questions?

From what I can gather from the Walstad method of low tech dirt tanks, is that leftover remnants of fish food will break down and keep the dirt rich with nutrients for the plants. At what level do you need to overfeed to accomplish this? does all of the detritus really break down and work it's way into the roots, or am I over simplifying it? This thought came to me recently because I've been planting a lot of vegetable seeds in containers so I can use them in my garden this spring. All the potting mixes and seed starting bags say they will feed for 4 to 6 months. I use Miracle Grow Organic Choice Potting Mix in my dirt tanks. I'm thinking that I don't have enough fish food waste rejuvenating my dirt, than the dirt isn't doing me much good. Thoughts?
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post #2 of 8 (permalink) Old 03-18-2013, 12:22 PM
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fish waste wont really replenish your dirt. the only time it might is if you have a substrate with a high cation exchange capacity, but even then, i don't know if it would actually translate into nutrients that the plants can use. i have heard people argue that point both ways, and i have never actually tested the idea myself.

many plants can pull nutrients directly out of the water column. those that can are the ones that would benefit most from the fish waste. i wouldn't suggest overfeeding your fish though, it usually leads to an unbalanced and ugly tank, not to mention problems with the fish that arise from a dirtier tank. if your substrate seems to start failing, i would stick to root tabs if i were you.
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post #3 of 8 (permalink) Old 03-18-2013, 01:49 PM Thread Starter
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Yeah , I agree with you on all points, but doesn't the walstad method suggest the dirt will last for years with no effort other than heavy feeding?
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post #4 of 8 (permalink) Old 03-18-2013, 04:26 PM
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A good soil layer will last several years without hiccup for most and looking at what I pay for food products I can't ever see overfeeding just to support plants.

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post #5 of 8 (permalink) Old 03-19-2013, 02:02 AM
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I may be missing the point, but you could also just stick some osmocote capsules in the dirt every several months. Sure it isn't fish food, but why put in cheap food with the intent of using it as ferts when you could put in even cheaper ferts?

Always curious.
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post #6 of 8 (permalink) Old 03-19-2013, 10:50 AM Thread Starter
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True true. To be honest with you, by the time I think my dirt is pretty much all "worn out" I'm about ready to tear the tank down anyway because I'm tired of it and want to do something else. My oldest tank running right now was dirted almost a year ago, it has two big Sword plants, and a full carpet of dward Sag, I dose liquid ferts in it too. I'm bored with the look, I might just tear it down and use fresh dirt. I want to grow really big Sword plants, so I think they'll appreciate the fresh nutrient supply in new dirt.
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post #7 of 8 (permalink) Old 03-19-2013, 05:44 PM
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Dirt, ADA As etc, these will decline after a year or two in terms of nitrogen, the other nutrients will last maybe a decade? Not sure, I'm not going to wait that long either.

Fish food can supply most of the N as NH4 and NO3 if the bacteria get it first(not likely).

I think for a typical CO2 enriched tank, the fish waste would have to be quite high to destabilize things. But since we have 10-20X slower growth in non cO2 tanks, the demand can be met.

I do not think you need to over feed though, just keep a nice stock and feed routinely, add extra algae eaters if you want to add more waste/food etc. They at least do something and will convert the waste into NH4 faster.

Tom Barr
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post #8 of 8 (permalink) Old 03-20-2013, 04:27 AM
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+1 on Root tabs/ Ferts, but if your using Walstad, it's probably your trying to sway away from those.

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