Go with the biggest tank you can afford, for a start.
Now, if you want vampire shrimp (atya gabonensis) you could have wood shrimp/bamboo shrimp as well.
You DO need to keep an eye on the GH and KH of the water, if its very acidic it will affect their exoskeleton and they will die, or have problems with moulting.
That said, i keep my pair in a fairly soft tank, but the buffering capacity of the water is pretty good, i add cuttlefish or similar to the filter which i think helps.
Vampire shrimp are big and clumsy, they WILL require an open space with easy access to a hiding space, they seem to prefer a sand substrate which means they can fit themselves under bogwood etc quite nicely.
Bamboo shrimp are much more nimble and will sit up on things to get their filter fans into the current, and get their food this way. I would still amke a point of feeding thems pecifically a few times a week with crushed flake and a turkey baster. These guys like something grippy to stand on and ive found rock is better than bogwood for this, real rock, not that fake stuff....
So if you go for those two with a sand substrate, you need a decent current in the tank and a fair bit of plant cover - bright tanks mean you wont see this little lot much. Plant cover that disperses the light means they will be more active, as does placing the tank somewhere its not going to get knocked or have kids and dogs etc bouncing around near it.
If you do this and have the sand substrate, then you could have some eels, i keep a pair of m. zebrinus with my shrimp and this is fine, neither are interested in the other, neither are capable of hurting the other.
I would go for a fair number of the shrimps, 2 or more small eels, as your main features.
Fishwise, if you have too many tetra types then its likely they will out compete the eels for food, and possibly the shrimp.
Id go for ottocinclus, and possibly cory cats (find the less frequently see types) for clean up and algae control.
Avoid like the plague any big plecs, they DONT like to share their space with bumbling clumsy shrimps and they will stress teh shrimps out of their hiding placse at shedding time when they are most vulnerable, and kill them!
After that, id go for a fairly peaceful type of fish, just one type and one that is not too voracious, i like boesmanii rainbows but im not sure theyd fit with the rest of the tank on water quality requirements - they are certainly not that common in home aquaria though and will be pretty to look at when the other fish are hiding.
Hth
Em
