Structuring For Varying Heights In Aquascaping: Will This Work?

I just purchased a 150-gallon aquarium that is 48x24x30", which is very tall, but it was on sale and ended up being cheaper than a 75-gallon with quite a bit less height and width: I plan on filling this tank about halfway, then using the rest of the height for plants to grow out of the water with only their roots submersed. Once I test the tank for leaks I will start a build thread.

Anyway, I want to have varying substrate heights. I should clarify that I don't want much in terms of slopes of substrates; instead, I want sand on the very bottom, then aquatic plant soil/gravel at an elevated level, and then something to keep the soil from spilling over and falling down into the sand. Instead of using tons of substrate piled up (which seems like a bad idea), I want to use some sort of lightweight - but not buoyant - material that I can put the substrate on top of so that I don't have to create a massive pile. I'll also need to use something to hide the sides of this material structure, which could either be rock or driftwood or something. Or, something that might work with fewer potential problems would be my plan that I list below.

The problem is that I don't know exactly what materials to use to accomplish this, but I do have a plan that might work. Key word is 'might', so I'm asking here to find out two things: whether my plan is good, or whether there are better ways to go about doing this. Here's my plan:

1. Create a 'shell' of rock/driftwood. This will be the part that is visible to observers, so this will be the main landscaping part.
2. Fill in gaps/cracks with fish-safe spray foam, but leave small cracks toward the back corner, allowing nothing but water to flow through. More on this topic later.
3. Use the same spray foam to fill in the space under the rocks, so that it creates a flat wall of foam.
4. Put a plastic sheet up against the foam wall before the foam sets, which will make maintenance easier should anything get behind the scape: there will be a flat wall of plastic rather than a bumpy wall of foam, so siphoning up whatever needs siphoning would be comparable to siphoning up waste beside the side glass of the aquarium. Very easy.
5. Since Steps 3-4 might require a lot of foam to accomplish, it'd probably be better to use a small amount of foam and just put the plastic sheets up against it, making sure that the bottom sheet is vertical, then having a slanted one above it to support the scape above it without having to fill the entire massive area under the scape with foam.

When completed, there will be an empty area at the back corner of the tank, which would be just filled with water. It will provide an area to put potted plants in, plants that will grow above the water's surface. Fish won't be able to access the area, unless they jumped really high or something haha. I'd build up rock/driftwood out of the water to create a wall so that fish can't jump over, but also so that you can't see the pots that the plants are in.

My biggest concern was that if I didn't have such an area, there'd be a 'void' under the scape where if anything were to end up there, such as fish waste, it'd be impossible to clean it unless I tore down the entire scape to access it. And I obviously do NOT want to do that. That is my main concern with this aquarium so I made sure I have a way to deal with it. Back in Step 2 I mentioned leaving small cracks to let water through - this is so that the empty area is connected to the main aquarium water section, so that there is no stagnant water anywhere. The cracks would probably be covered with a fine screen just to prevent waste from flowing through, but these cracks would be placed in such a way that you can't even see where the cracks are.

So that's my plan. If you read all this, good job, because it's long... I added stuff to this thread as I came up with new ideas while writing it. My goal is to have a beautiful aquascape with little to no potential for any problems whatsoever.

 

You could do a really awesome paludaroum set up with this size tank if you wanted to also add some critters that like time out of water as well as in (frogs, salamanders, snakes etc).
While I like the idea of the hidden area for the plant roots, I do wonder how well water will filter back there to feed the roots? My concern is that they will become dead spots in the aquaroum. There's water there, yes, but not enough flow to keep the water moving through there. Perhaps a small powerhead back there, or mear the slits to keep water moving there would be a good idea?
Have you considered a waterfall feature? You coukd have a power head hidden back in the area with the plant roots that sends water up to the top of the hardscape structure and then it will flow back down the fron back into the main body of water in the tank. This would provide extra aeartion to the water, and the powerhead would create suction to draw more water back into the area for the plants to feed off of.

 

I just wanted to tell you that ive been considering something like this and just thought to put wide and low pots from Home Depot...either upside down, or right way, or one on top of the other..if they are upside down, it is possible to make a cave for fish in there at the same time...I never tried it, so its just an idea, may be not doable

 

Lava rock is good for this. I think Dennis Wong and George Farmer on youtube have a couple tanks that look like what you're talking about.

 

You could do a really awesome paludaroum set up with this size tank if you wanted to also add some critters that like time out of water as well as in (frogs, salamanders, snakes etc).
While I like the idea of the hidden area for the plant roots, I do wonder how well water will filter back there to feed the roots? My concern is that they will become dead spots in the aquaroum. There's water there, yes, but not enough flow to keep the water moving through there. Perhaps a small powerhead back there, or mear the slits to keep water moving there would be a good idea?
Have you considered a waterfall feature? You coukd have a power head hidden back in the area with the plant roots that sends water up to the top of the hardscape structure and then it will flow back down the fron back into the main body of water in the tank. This would provide extra aeartion to the water, and the powerhead would create suction to draw more water back into the area for the plants to feed off of.

Hm good point about the water movement. This is the kind of thing I wanted when I posted this thread -- someone to give me tips and help find potential problems so that they can be averted before they even happen.

I have considered the paludarium setup for land animals but I thought I'd have to dedicate too much land to the non-aquatic creatures which might take away from the of the final product that I had in my mind. I thought of maybe getting frogs particularly because I thought they'd be cool, but then realized they'd probably trample my delicate arrangement of plants out of the water. Plus, in my setup, they could get stuck in the empty back section, which I thought would be silly for the frogs to have access to. But maybe I could put a screen back there that I can remove if needed, which would provide a little platform for them to rest on at the back, and just make sure none of the frogs are under there when I put it back in in the case where I needed to take it out.

A waterfall feature? That's an awesome idea. I was actually thinking about it but didn't know the best way to implement it. In fact I was thinking of creating a new thread for it. Would it be best to use a pump with a hose attached that will intake water and then pump it through the hose over the scape? If that's what I'd do, how do I prevent back-siphoning?

Ok, you got me thinking! What if I provided a good section of land for poison dart frogs or something, then a removable screen/platform at the back where the land-based plants can rest on, which would prevent the frogs getting under there, then a powerhead for circulation and/or a pump to use for a waterfall feature?

Natalya and -Mak-, thanks for your replies as well: I think lava rock would be good for scaping, but wouldn't its porousness cause areas for waste to get trapped in? And natalya, if you end up doing something like you said (since you said you were considering it), let me know and I'll check it out.

 

Hm good point about the water movement. This is the kind of thing I wanted when I posted this thread -- someone to give me tips and help find potential problems so that they can be averted before they even happen.

I have considered the paludarium setup for land animals but I thought I'd have to dedicate too much land to the non-aquatic creatures which might take away from the of the final product that I had in my mind. I thought of maybe getting frogs particularly because I thought they'd be cool, but then realized they'd probably trample my delicate arrangement of plants out of the water. Plus, in my setup, they could get stuck in the empty back section, which I thought would be silly for the frogs to have access to. But maybe I could put a screen back there that I can remove if needed, which would provide a little platform for them to rest on at the back, and just make sure none of the frogs are under there when I put it back in in the case where I needed to take it out.

A waterfall feature? That's an awesome idea. I was actually thinking about it but didn't know the best way to implement it. In fact I was thinking of creating a new thread for it. Would it be best to use a pump with a hose attached that will intake water and then pump it through the hose over the scape? If that's what I'd do, how do I prevent back-siphoning?

Ok, you got me thinking! What if I provided a good section of land for poison dart frogs or something, then a removable screen/platform at the back where the land-based plants can rest on, which would prevent the frogs getting under there, then a powerhead for circulation and/or a pump to use for a waterfall feature?

Natalya and -Mak-, thanks for your replies as well: I think lava rock would be good for scaping, but wouldn't its porousness cause areas for waste to get trapped in? And natalya, if you end up doing something like you said (since you said you were considering it), let me know and I'll check it out.

Oh, the lava rock is for putting underneath the substrate. It'll keep it in place better and you'll use less actual substrate, which can be very expensive.