gravel mounds - The Planted Tank Forum
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post #1 of 9 (permalink) Old 06-11-2013, 05:22 AM Thread Starter
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gravel mounds

I have about 2 inches of pool filter sand as the substrate of my tank. I was wondering if i could put mounds of gravel to make a "mountain" type aquascape. Would any type of anaerobic bubbles form under those specifically very thick areas? Are there any downsides to doing this like, making cleaning difficult.
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post #2 of 9 (permalink) Old 06-11-2013, 12:00 PM
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They will have to be reset every few weeks, more or less..

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post #3 of 9 (permalink) Old 06-11-2013, 04:11 PM Thread Starter
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why would they have to be reset. I dont have any fish that would move the gravel
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post #4 of 9 (permalink) Old 06-11-2013, 04:34 PM
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Depending on the depth you could potentially have issues with a dangerous type of gas forming if there is no flow, sorry I forget the name of the gas. With regards to gaining height a good technique I picked up from is to use substrate supports.

I bought some from them which cost a fortune for what is essentially just corrugated plastic, you could easily use other cheaper forms of plastic or even thin rocks like slate to form vertical walls underground. This will stop the height you are gaining from slipping down and is also a useful way to form a barrier if you want to stop certain plants from spreading into different areas..

It is worth watching some of their demos on the link, they did show you how to combat the gas build up problem in one of them by using different sized substrates in layers, though I forget the exact technique.

As for cleaning, well yes even with the supports you are going to disturb the surface to an extent and so it will require either great care whilst cleaning, or a bit of maintenance at times.

Perhaps using vertical rocks as wall like barriers for your substrate, with the tips poking out would give even more of a natural mountain feel?
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post #5 of 9 (permalink) Old 06-11-2013, 09:02 PM
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I'm guessing that steven p was hinting that the slopes will flatten after a while.

I don't think there is much of a concern with anaerobic pockets unless you are sticking something organic underneath there. And even so, if you have plants in the tank, they will probably end up putting roots all through the substrate and lessening the danger (Walstad has a section in her book about it).

I've seen people use inert substrate (gravel, etc.) stuffed into nylons to form pillows/sandbags to take up dead volume (don't waste the expensive stuff), and build contours, and then add the nice substrate on top.

I've never done much with slopes, but if you can put in some sort of barrier like Jonny said, it should help prevent the leveling out. Some substrates will probably be better at holding a slope - anything with rough/angular grains will be more resistant to leveling, but I don't have enough experience with slopes to give any specific recommendations.
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post #6 of 9 (permalink) Old 06-13-2013, 02:59 AM Thread Starter
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Thank you all for the replies. I think i will use rocks covered with substrate to create the build up.
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post #7 of 9 (permalink) Old 07-02-2013, 03:21 PM
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I've tried burying things to make hills and mounds, the gravel will eventually shift and flatten. I've had greater success using pieces of 1/4-1/2 buried driftwood to make retaining walls instead. Sorry, I hope this isnt too late! Works great for me!
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post #8 of 9 (permalink) Old 07-03-2013, 05:11 AM
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I use rocks and expanding foam filler (pond supply) as mortar to make a solid retaining wall. Anything less (gaps between the rocks or driftwood) will allow the fine substrate to equalize or level out.

I would not cover sand (even PFS) with gravel. If you want a deep bank of gravel, then just use gravel. Plants will grow in that as well as they would in sand.
I have smelled anaerobic spots in sand (PFS or similar, I do not use play sand) when it is covered by a large decorative rock. I think the same thing would happen if it was covered in gravel.

If you are still worried you might put a bubble wand under the mound, all the way to the bottom of the tank. This will create some water movement through the gravel.
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post #9 of 9 (permalink) Old 07-03-2013, 01:43 PM
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A bubble wand buried under a hill would cause crazy erosion no?

A friend of mine with very very deep substrate areas has solved this problem by using undergravel heating. The rising warm water pulls fresh water through the gravel.

Great idea with the pond foam!!!
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