Try to physically remove as much of the green “stringy” algae as possible - try to “catch” the strings in a toothbrush or similar, use a narrow syphon hose (syphon to bucket so you can return any accidental shrimp to tank), gently brush through the hairgrass with a “pick” comb
If it’s in the moss, just trim the moss back to the wood etc (I think you mentioned moss pieces breaking free?) - if you cut off any significant lumps of moss, you can comb through to remove any algae, then sparingly glue/tie to wood etc
Jurij mit JS has a couple videos demonstrating moss glue techniques
For tying moss, ADA-japan has some video (there’s an excellent video for moss tying, followed by trimming of the moss tightly to the wood, somewhere, I’ve just never bookmarked it
😳 
)
Re your Otocinclus, find an alternate source - these fish are obviously unwell (sick to death
🙁)
Shrimp that inadvertently end up in the filter, generally manage just fine as long as the filter is running (good oxygen levels), just remember to check for them when you clean the filter
With more than a couple Oto’s in a 45P, you’ll need to supplement food
I just use snails in smaller tanks, while the larger Nerites are terrific (horrific) egg layers - and those little white egg “shells” are well and truly glued in place
😱 - I’ve yet to see any egg debris from my Clithon corona snails (after 1-2 years)
I’ve also some “Batic” nerites that seem unlikely egg producers (they are a smaller Nerite and I’ve seen nothing of note after several months)
I no longer add Amano type shrimp as they can be relatively aggressive, quickly develop a strong preference for fish food, and grow relatively large ...
i went to dobbies and another 2 shops that i remember however none had any fish as 2 were shut and dobbies dont have aquariums anymore so ended up at pets at home just minutes away 
after driving round for hour and a half, i should have checked. 
