Zebra Danios With Other Fish And Shrimp

Hello all! I recently acquired a US 20 gallon tank with an oversized external filter. After cycling it for 6 weeks, I added 7 zebra danios and one betta, as well as two assassin snails to help with a snail infestation that had come in with some plants. Now, at the time I got the fish, I did so on the understanding that the danios were perhaps prone to nip the betta if there weren't enough of them. Fortunately, this has not been a problem. The betta ignores the danios, they ignore the betta, and everyone is happy so far.

My question goes to what might happen were I to add some Amano shrimp to the mix. Would this be a problem? I don't wish to add shrimp just to have them eaten.

I'm considering as the next additions a small group of harlequin rasboras and then later (as the final addition) some pygmy corydoras, and would appreciate any insights, or perhaps better suggestions.

Thank you!

Tanks with bettas in are very hit and miss. I have had three bettas with shrimps, although these were cherry shrimps which are smaller than amanos. The first of the three was very laid back so i moved some shrimps from my main tank. He ignored the adults and baby shrimps to the extent that the population expanded and I was finding baby shrimps in the bucket at every water change. After that betta died, I bought another. This betta ignored the adults but I no longer found babies in the bucket and the shrimp population remained stable.  The next betta (which has just died) attacked and ate the shrimps. I kept finding bits of shrimp all over the tank.
With amanos, there won't be any baby shrimps as they can't breed in fresh water, and they are larger and less colourful than red cherries so they might work.



But it is my duty to the fish to warn you. Danios are fast swimming fish and they should not be kept with slow swimming fish such as bettas or harlequins. Fast swimming fish stress slow swimming fish just by their behaviour.
And bettas are not community fish, they should be kept alone. So many people think the fish are getting on OK then one or other snaps (often the betta) and that fish goes on a killing spree. If you can find somewhere to fit a 25-ish litre tank and move the betta into that, it would be much better for the betta and the other fish.

Thank you for your help!

Since reading Sue's reply, I've been observing the fish even more closely than usual. I have concluded that my betta is living like he's surrounded by noisy teenagers, and though my tank is heavily planted, so provides numerous places where he can get away from them, he still would probably be happier on his own. To that end, I've ordered a new tank for the betta and will add different fish (for instance, cherry barbs) to the existing tank with the danios at some point in the future. I'm quite fond of the betta and don't want him to be stressed out. And of course, I don't want murder in the tank, either.

I can't reply tonight, unfortunately, but will endeavour to do so tomorrow.

Apologies for not having replied before now but my advice would have been the same as Sue's.
Great to read that you have a new tank planned for the betta.
Cherry barbs are a feasible option with the zebra danios, and they are lovely fish, so that sounds like a good plan - their temperature requirements do overlap as well as activity levels being closer than your previous thought of harlequin rasboras, while Littlefish's suggestions are good possibilities too (there's a golden version of the WCMM as well).

Rama is lovely. 
I think you are doing the right thing by getting him his ow place. I'm sure he'll appreciate it.
If you use the mature media from your existing tank you don't have to go through cycling the smaller tank for you betta. You can move him in as soon as the tank is set up.

Oh wow - what an absolute beauty Rama is!   

Glad you're getting the optional extension for the filter.  I actually bought that filter as a back-up for my hospital/QT on the basis of good reviews about how gentle a flow it had and how silent, etc, but found its design didn't accommodate other media; however, the extension module entirely addresses that issue, and isn't that expensive, so thank you for mentioning that as I hadn't realised it existed!