Substrate Depth

[manwithnofish]

I have a 70 gallon fw planted tank. It measures 36"l x 18"w x 25" h. I decided on a mixture of Eco-Complete and Flourite. I'm pretty sure I used 40lbs (2 bags) of Eco on the bottom, then 3 bags of Flourite (45lbs) then I mix one bag of each for the top. I mixed it for asthetic appeal (I liked the mixed colors). So all together, I have 120 lbs of substrate which is pretty much what the online calculator suggested. It amounts to 4" deep on average. I made it that deep in part because my tank is so tall. Some hobbist have cautioned me about methane and Hydrogen Sulfide gases while others proclaim this as a disaster in the makings, suggesting that I remove half the substrate. I've read as many articles as I could find, and the depth was not outside the suggested guidelines.

I concede that the production of these gases are natural parts of an aquarium's substrate and is less of a concern in shallower substrates. But I expect there are ways to mediate any potential problems.

Ok this has gone from being a relaxing hobby to a "more than I ever wanted learn about chemistry" exercize.

According to what I am reading from Diana Walstad's book (text from book):
(1) H2S (Hydrogen Sulfide), a resulting byproduct of anaerobic decomposition of organic matter (in the substrate) can be extremely toxic to plants, but not fish because it is oxidized immediately in the presents of oxygen in the water. H2S is oxidized aerobically by chemoautotrophic bacteria. So my take on this is that there's probably no need to worry about the H2S unless I see all my plants die.

(2)Methanogenisis is the process where Methane is produced by anerobic bacteria in the breakdown of organic matter during the fermentation process and is released from the substrate and enters the water. Methane-oxidizing bacteria are apparently plentiful in the tank (on the surface of the substrate ) and quickly breakdown the Methane. I think this takes care of the Methane being released by diffusion (slowly) into the water. Aquatic plants facilitate the breakdown of the Methane by increasing the amount of the oxidizing bacteria. So the danger is in gas pockets or bubbles that might accumulate in the substrate and then for some reason result in a sudden and large release of Methane. How can we mediate the danger of this happening without taking an eggbeater to the substrate?

I don't think I need to nor do I want to remove any of the substrate, but I will if it is doomed for failure. So what do you think?

 

[Madam Macaw]

I have a 70 gallon fw planted tank. It measures 36"l x 18"w x 25" h. I decided on a mixture of Eco-Complete and Flourite. I'm pretty sure I used 40lbs (2 bags) of Eco on the bottom, then 3 bags of Flourite (45lbs) then I mix one bag of each for the top. I mixed it for asthetic appeal (I liked the mixed colors). So all together, I have 120 lbs of substrate which is pretty much what the online calculator suggested. It amounts to 4" deep on average. I made it that deep in part because my tank is so tall. Some hobbist have cautioned me about methane and Hydrogen Sulfide gases while others proclaim this as a disaster in the makings, suggesting that I remove half the substrate. I've read as many articles as I could find, and the depth was not outside the suggested guidelines.

I concede that the production of these gases are natural parts of an aquarium's substrate and is less of a concern in shallower substrates. But I expect there are ways to mediate any potential problems.

Ok this all this has gone from being a relaxing hobby to a "more than I ever wanted learn about chemistry" exercize.

According to what I am reading from Diana Walstad's book (text from book):
(1) H2S (Hydrogen Sulfide), a resulting byproduct of anaerobic decomposition of organic matter (in the substrate) can be extremely toxic to plants, but not fish because it is oxidized immediately in the presents of oxygen in the water. H2S is oxidized aerobically by chemoautotrophic bacteria. So my take on this is that there's probably no need to worry about the H2S unless I see all my plants die.

(2)Methanogenisis is the process where Methane is produced by anerobic bacteria in the breakdown of organic matter during the fermentation process and is released from the substrate and enters the water. Methane-oxidizing bacteria are apparently plentiful in the tank (on the surface of the substrate ) and quickly breakdown the Methane. I think this takes care of the Methane being released by diffusion (slowly) into the water. Aquatic plants facilitate the breakdown of the Methane by increasing the amount of the oxidizing bacteria. So the danger is in gas pockets or bubbles that might accumulate in the substrate and then for some reason result in a sudden and large release of Methane. How can we mediate the danger of this happening without taking an eggbeater to the substrate?

I don't think I need to nor do I want to remove any of the substrate, but I will if it is doomed for failure. So what do you think?

I am curious to see the responses you get also - nice post.

 

[wolfwolf]

My thoughts....

Gas build up is only a problem with very fine substrate (like sand).

I've never heard of having 4" of substrate. Why would you do that?

 

[vinylman]

Two to three inches at most, I'd say, but nothing to do with gas build-up; that should be more than enough to plant anything you'd want, plus any more than that is just using up space without needing to. I use around two inches of Aquagrit which is much lighter than gravel or other substrates and never had trouble with planting.

 

[manwithnofish]

Ok, I Google Searched "Depth of Subtrate in Aquariums" and copied this from the first 3 in the search list. I didn't research it, I just took the first 3 it found.

<a href="http/www.wetwebmedia.com/PlantedTksSubWe.../substraags.htm" target="_blank">http/www.wetwebmedia.com/PlantedTksSubWe.../substraags.htm</a>
Back to the item at hand, gravel depth. Hmmm, here's a statement: "Depending on substrate particle size, use of soils, plant species mix... and more, a depth can be either too much or too little". Too much is a functional definition, by which I mean that anaerobic conditions produce too much in the way of anoxic by-products, causing stinky troubles for your livestock. Too little depth, and you don't get the mostly anaerobic benefits.
Don't give up on me yet. In practical terms we are talking about a few inches of substrate, oh two to four, five inches. Larger grades may be deeper and still afford minimal circulation to plant roots and diffusion of chemical reactions of purpose to the aquatic gardener.

<a href="http/www.aqua-fish.net/show.php?h=aquariumsubstrate" target="_blank">http/www.aqua-fish.net/show.php?h=aquariumsubstrate</a>

This lower layer should be high enough to cover the roots of the plants, up to two inches.

As for the top layer, you can use regular gravel or even sand will do nicely, and it should be one and a half to two inches in height.

<a href="http/www.thekrib.com/Plants/Fertilizer/s...ate-randall.htm" target="_blank">http/www.thekrib.com/Plants/Fertilizer/s...ate-randall.htm</a>
Then I wash the rest of the gravel and spread it carefully over the bottom layer. I used to start with at least a 2-3" depth in the front, with up to 5" in the back where I intended to place large plants with extensive root systems. If you decide to slope the gravel this way, you will have to build terraces with rocks to hold the gravel back. Otherwise, the gravel will slowly but inexorably level itself out. Nowadays, I don't like to give plant space over to the rocks needed for terracing, so I place about 3-4" of substrate level in the entire tank and do my "terracing" by using plants of different sizes.

Remember My tank is a Planted Tank, 25" tall.