If there is space, you could have Amano and cherry shrimps in the same tank if you choose to. Amanos generally are peaceful, but being larger, they will eat smaller shrimp, particularly baby shrimp, if they find any. I can attest to that personally. Amanos also can't have baby shrimp in your tank, as they have larvae that require brackish water for a month to morph their larvae.
If you do decide to mix them, it helps to provide many small hiding places. Plants are great for that, but so are rocks and wood pieces, you can use smaller ones for a small tank.
You might like to get another colour of small shrimp instead. Most shrimp eat some algae, though not all of them are algae specialists. For example, with Cherry shrimp, you could also have Babaulti shrimp, as they can't cross breed with Neos. They come in green and several other colours. Or perhaps Orange Bee shrimp, which are not a true Bee shrimp but Caridina propinqua, aka Sunkist shrimp. They also can't cross breed, and also have larvae instead of baby lookalikes, needing brackish water for their larvae to be able to survive and morph to the shrimp form.
But they can provide a charming colour contrast, with cherries or any of the other Neocaridina shrimp colour forms.. including yellows, blues and even chocolates. Yellow shrimp can often be had for not a whole lot more than cherries. There is also a dwarf type of fan shrimp.. Atyopsis spinipes, comes in a few colour shadings, wild form and one called Golden Fan, that resembles a tiny Bamboo or Flower shrimp. They prefer some current to feed in, as they filter food with the fans on their front legs, but unlike the larger filter shrimp, they seem fairly content feeding from the bottom as well. But best to have at least some current and fun to watch them wave their fans and then wipe them across their mouth to get the food bits off the fan bristles.
You should know Cherry shrimp come in several colour grades. The wild form is nearly colourless, brownish mainly. The higher the grade.. ie: the redder the shrimp, the more it will cost. Fire red, Painted Fire Red and Bloody Mary are names for colour grades in cherry shrimps. Tommy at Shrimpfever can tell you everything you ever wanted to know about shrimp, and is a really nice guy too.
The issue with Otos, other than tank size, is that they are obligate algae eaters. The Germans call their diet 'Aufwuchs', meaning the layers of soft algae growing on underwater surfaces plus the tiny animals that live in this algae layer. In tanks it's very hard to provide this diet, and the fish end up living mainly off biofilm. A new tank won't have enough biofilm, it can take up to six months to have enough of it.
And Otos are a lot like cows, in that they use gut bacteria to digest the cellulose in that algae. They're wild caught, and while being held and shipped, they are not fed. This causes the gut bacterial populations to die off, not unlike what happens to humans if we have to take antibiotics. But the fish end up in a store tank where there is no food they recognize, and even if they are willing to eat algae tabs, which many are not, they won't have the bacteria to digest it for weeks or months.
If you get a larger tank and want Otos, best to buy them only after they have been in the store for a minimum of one week, and 2 or 3 is better. By then, the weakest have died off, leaving the strongest ones. If they survive about two months in your tank, chances are they'll live for many, many years. But many do not live two months, some not even two weeks. Four to six weeks seems to be the most critical time for them once you get them home.
I've been growing algae on marble chips for the Otos I have. It takes a LOT of chips to keep them happy, they can clean one off in a few hours. I keep the chips in a jar of tank water in my sunniest window, and outside in summer. Snails also appreciate this algae and there will be competition for it if you have snails as well as Otos.
Having something in a tank that will eat algae is not always a necessity. First find out if you have an algae problem, before you assume you must have an algae eater. Many algae issues are either self limiting or related to lighting or feeding of the tank and can be corrected. And snails of several kinds can actually be better at keeping tank walls clean than many shrimp or fish are.
If you really want some fish moving around, especially in the upper part of the water column, there are some pretty nano size fish that will be content with five or so fish to swim with. Chili rasboras, though they can be very shy; Celestial Pearl Danios; Daisy rice fish also are very pretty, though their colours are a bit more subtle and easier to appreciate closer up. Of the three, I think the chilis are the most likely to stay in the upper waters. CPDS seem to like mid water levels best, and I haven't have Rice fish long enough to really tell if they have a preference for one level over another, but in the store tanks they are usually in the upper half to two thirds of the tank.
With CPDs, you're best off with groups with roughly 3 females to one male. Both have colour, but males are darker blue, females paler blue. Sometimes people want all males because of the colour, but it's hard on the boys if you do that. Males will spar with one another if there's more than one of them, so dense plantings or decor help break up sight lines to reduce stress between competing males.
With any fish that school or shoal, I try to have groups with approximately one male to 2 or 3 females unless it's known some other ratio works better, such as pairs only. I think the fish are better off for it, and you will see more of their natural behaviours. In tanks with more space, where you can have more than one group, you also get to see the interactions between males and females, especially with fish that are a bit more territorial.
