Corydoras and sand

I'm finally at the stage where I can start to properly plan and get bits for my new 280 litre, and I have a few questions.

Maximum sand depth?
If the minimum sand depth is around one inch, is there a maximum? I am thinking of doing a cool aquascape with areas of deeper substrate and greater height, but I've heard something about toxic gas build up or bacteria? I know very little about this, and I don't know which internet sources to trust other than you people here at TFF. I've put in two pictures I've found online that I like how the substrate is arranged, in terms of placement and depth variation. I've seen people say to keep sand depth under 3", but I don't understand why. Won't plants like amazon swords need substrate depth for root growth?
I know the sand will settle a bit, but I want to achieve height layers without obvious walls of rocks and stones. I don't know how else I could add substrate height in areas.

Corydoras and sand surface area
I know that sand is important for corys instead of gravel substrate, but how much room do they need? I want to have lots of beautiful hardscape and plants, and I don't want to leave the corys without enough sand to do cory activities. The tank is roughly 120cm long and 40cm wide (60 cm tall.) Would about 1/3 be too little of open sand area?

Corydoras and carpeting plants
So far from what I've read online, it seems like carpet plants get disturbed and destroyed by some cory species. Would an area of established carpeting plants be an option with corys? Ideally there would be areas within the tank that are heavily planted, some areas sparsely planted and an area with no plants at all.

Corydoras and root tabs
For any root feeding plants, I'll want to have root tabs in the sand. How deep would they need to be in the substrate so that corys won't move them? Maybe I've over estimated their digging and sand moving capabilities.

Thanks for looking at my questions so far, any advice would be appreciated!

rebe said:

I know the sand will settle a bit, but I want to achieve height layers without obvious walls of rocks and stones. I don't know how else I could add substrate height in areas.

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Use a can of spray foam to build up in the corner. You can also wrap a rock in plastic, hold it up using a small piece of pvc pipe and spray foam under it.

I use polyurethane gorilla glue, cover a surface and put substrate over it . So the foam will have a thin layer of substrate over it.

rebe said:

I know that sand is important for corys instead of gravel substrate

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Most people would choose sand when they have cories. I have some tanks with sand but most have gravel or substrate. As long as the gravel or substrate have a smooth surface, there's no problem keeping those with cories. I've done this for many years now. And they all do well and even reproduce. But with sand, the risk is zero to damage their belly.

First point is that all cories need sand as they are filter feeders. So it is one of whether or not you care for the fish to provide what they expect. We'll assume that is a "yes," so that brings us to the other issue with gravel mixed in with sand. A cory is not going to know gravel is harmful, so if it is there is is more likely to affect them, And the "harm" is usually more a bacterial problem than rough gravel.

On the other questions, I never had issues with cories and root tabs and I had them regularly. As for carpeting-type plants, this depends upon the type of plants. All I ever had were large swords, crypts, and the pygmy chain swords which left lots of open space; the photo below was my last tank with 40 cories.

madmark285 said:

Use a can of spray foam to build up in the corner. You can also wrap a rock in plastic, hold it up using a small piece of pvc pipe and spray foam under it.

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That's a really good idea! In your experience, would sand layered on top but not stuck on eventually move down off of the build up area and settle at a lower level of the tank?

emeraldking said:

But with sand, the risk is zero to damage their belly.

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Awesome, that's what I was thinking.

I got two bags of the best play sand in Ireland for aquarium use (according to blogs and people's experiences online). 40kgs all together, but I may or may not need it all. Such a good thing to use play sand instead of decorative aquarium sand. In the place I was at, it was either €23 per 2KGs of aquarium sand or €12 for 40KGs play sand.

Byron said:

I never had issues with cories and root tabs and I had them regularly. As for carpeting-type plants, this depends upon the type of plants. All I ever had were large swords, crypts, and the pygmy chain swords which left lots of open space;

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That's good to hear, thanks for sharing your experience. I like the pygmy chain swords, I might look into those as a possibility. It's really good to see the image of your 40g cory tank, it looks beautiful.

Is this tank suitable to quarantine a bolivian ram and some julii corydoras?
They are small juveniles, I am going to a place that has them next week and I wanted to make sure before I got them. The bolivian ram would only have been around 2 inches.
The tank is 54 litres with dimensions of 60x30x30 cm. It's been up and running for over a month now, and ready for fish I believe. (The plants all have new growth and look healthy, and with bladder snail bioload there is no ammonia or nitrite with tap water levels of nitrate. I will put a load more of my floating plants for when I get fish, siphon out the snail poop and move the bladder snails.) It has a layer of aquarium sand, and then some java ferns, and anubias attached to rocks (for easy removal in case of medications etc). There are also some salvinia floating plants.

rebe said:

Is this tank suitable to quarantine a bolivian ram and some julii corydoras?
They are small juveniles, I am going to a place that has them next week and I wanted to make sure before I got them. The bolivian ram would only have been around 2 inches.
The tank is 54 litres with dimensions of 60x30x30 cm. It's been up and running for over a month now, and ready for fish I believe. (The plants all have new growth and look healthy, and with bladder snail bioload there is no ammonia or nitrite with tap water levels of nitrate. I will put a load more of my floating plants for when I get fish, siphon out the snail poop and move the bladder snails.) It has a layer of aquarium sand, and then some java ferns, and anubias attached to rocks (for easy removal in case of medications etc). There are also some salvinia floating plants.

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Yes on using this as a quarantine. [I take it you are only getting one ram, so that is fine; two might suddenly squabble.]