A few things:
Shrimp (and other invertebrates like snails, crayfish, and the like) need minerals for their shells. Fish also absorb these minerals through their gills. They get these minerals from the water. In a natural ecosystem like a pond, they are re-introduced in the way of rain, and runoff from the surrounding area as the rain water moves towards the ponds. For this reason alone, I recommend water changes regardless of whether the levels in the tank say you need it or not.
Also, without heavy filtration of some sort (you said you are using a submersible one rated for 55 gallon, which might not be quite enough), you will not be able to get the levels of feeders needed for both layers. You will need a sponge or something over the intake if you use a single filter, otherwise your baby shrimp/endlers will get sucked into it. I recommend at least double the "rated" filtration, if not more.
You might want to start a second tank if you have time/room, as 20 cherry shrimp might not be enough to sustain the system. That would be a good starter colony, but you want a full colony before adding the endlers, so you almost always have babies for the baby endlers to feed on. Normal spawn times are around a month, so my recommendation would be at least 24 females, if not 48, so you would always have babies being born. Right now, I'm down to 3 females, with slow spawn rates, as I screwed up the first 2 pieces of advice above and lost most of my colony...
As far as plants, I would put in some duckweed (may or may not last, as endlers devour it) and some pelia. Both are good food sources for guppies and endlers, and should help with the non-protein portion of their diet.
Hello there! Welcome and thank you for posting!
Worry not, as of right now I am performing regular water changes, not even just regular top ups. In addition, the hope is that by using a natural and organic soil as my base, the nutrients and minerals will make their way into the water column. If not, well than I am going to look into other long term solutions for this fix, such as putting some shells on/in the substrate.
Yeah I was thinking the same with the filtration. My hopes were that the plants themselves would be able to pick up any slack, but that assumption may be misguded as far as I know. I know that in a heavily planted tank, people have had reports of low ammonia/nitrates existing in their tanks, so that is something I am watching as the tank matures more. Im still as 0 ppm all across the board as of right now. I do have some filter sponge wrapped around all the intakes of the filter with the hopes of it stopping the babies from gettting sucked in. As of right now, Ive seen some smaller shrimp I got as well as small malaysian trumpet snails on it and doing just fine, so hopefully the baby shrimp would be ok.
I actually do have plenty more shrimp now, I ended up buying more and have 40+. Not that I could ever count them all anymore, but I bought 40+ more in addition to what I already had. From my understanding though, the baby endlers should not be eating the baby shrimp at all. I don't know if perhaps I am misunderstanding what you mean there. In fact, the endlers seem to be the most absolutely docile fish I think I have ever had. The males will still chase the females, but they seem less aggressive than the shrimp almost haha. They certainly get more scared of them than vice versa.
I actually did put some duckweed into my tank recently. Its even trapped in my little corral and yet the fish seem to ignore it. They go into the corral and pick some food off the roots of the plants, and when the duckweed escaped once they all got excited thinking it was food, only to be disappointed after the first nibble. So I dont know what's up with that. I expected the duckweed to be eaten honestly lol. Thanks for the idea about the pelia though! I will defintely be looking into that. Anything to make the fish more happy and give them a more natural home!!
Thanks again for the replies everyone! I love hearing other people's ideas and it was forums like these that inspired me to start my own project!