JettsPapa

Since you started with the Skynyrd, here is one of my top 5 favorite songs, of any genre.

Since you said they're tank raised, I assume they were raised by a hobbyist? If yes, I don't think I'd bother with quarantining them since they're less likely to be sick or have parasites. Much of that sensitivity (or maybe all of it) is due to most, if not all, of the ones available in stores being wild caught, and they often suffer irreversible damage to their digestive systems before reaching the store. After that they're just about bullet proof (or at least have been for me).

Otocinclus aren't bottom feeders, so I'd cross them off, at least for the time being since they need established tanks with plenty of biofilm. I'm a big fan of corys, and you have room for a good sized group. How large depends on the species, since they aren't all the same size.

On the other hand, I don't know if this applies to others or just me, but I seem to have considerably less algae in the larger tanks.

Unfortunately, that's no uncommon for commercially raised guppies. I assume you bought them from a chain pet store? If yes, I'd suggest trying to get some from a hobbyist breeder, or a locally owned store that buys from local hobbyists.

I don't know. All my tanks have inexpensive LED lights on 8 hours per day.

I agree that a sword would get too large. I'm a big fan of crypts, and there are some varieties that get large enough to make good background plants. Cryptocoryne usteriana and Cryptocoryne pontederiifolia are my current favors, and both would be good choices.

Here is a link to some information I put together for new shrimp keepers a couple of years ago that you might like to review. In any case, I'd encourage you to add more live plants, and give the tank more time to build up biofilm before adding shrimp.

Some of the larger rainbowfish, like Boesmani or turquoise, may be effective on small fry. I don't think they would bother larger guppies.

Unfortunately, commercially produced dwarf gouramis and neon tetras, along with guppies, are prone to health problems, and just not living long in general.

So the gunk that came out of the filter media went back into the tank? That's what it sounds like. If yes, you should discard that water and add fresh water back into the tank. Most people rinse their filter media in a bucket when doing water changes.

Unfortunately dwarf gouramis are plagued with health problems. I hope you can save the fish, but to be honest it would surprise me.

Just to be clear, are you changing the filter media, or rinsing it and putting it back?

It sounds like it has, assuming it was fully cycled to start with. Do 50% water changes whenever needed to keep ammonia and nitrites low, even if that means more than one per day (their toxicity depends on pH, but keeping the combined values below 1.0 ppm is a good rule of thumb). I wouldn't add any other chemicals or miracle bottles of bacteria (other than dechlorinator, of course). They aren't a substitute for water changes. Assuming your tank is fully cycled, rinsing both sponges shouldn't be a problem, but it might be best to only rinse one at a time until you get things under control. I assume you're rinsing them in water you've taken out of the tank? A quick rinse under a faucet isn't generally a problem in well seasoned established tanks, but you aren't there.

I found it.

My daughter-in-law had a 3-spot in a community that turned aggressive, and was terrorizing just about every other fish in the tank. She moved him to her African cichlid tank. He wasn't nearly as tough in there.

As mentioned above, leaving the old cartridge in the filter with the new one for a few weeks is a great idea, but you shouldn't need to change it very often. You can rinse in the the bucket when you do a water change to get most of the gunk off of it, and put it back. After your tank is well seasoned (6 months old or more), you can rinse it under the faucet, but I wouldn't do that yet. Don't replace the cartridge until the old one is falling apart. I know the directions that came with the filter say to change them often, but while I try not to be too cynical, I wouldn't be surprised if that has something to do with the same company selling the filter and the cartridges.

My best recommendation would be to stop adding chemicals to fix problems that could be better solved by doing water changes. Changing 50% or more of the water won't hurt a thing, and is the best way to keep the water quality in good shape.

I have lemon tetras with mine. They're also been just about bullet proof, and I think their colors complement the turquoise rainbows.

Maybe I should have explained better. When I said they weren't aggressive, I meant attacking tank mates, as opposed to grabbing food.

I have similar water. I've tried angelfish twice, but they've never lasted more than about a year. I haven't followed this whole thread, but I wanted to mention that I have a group of turquoise rainbowfish in my 65 gallon tank and really like them. As far as I can remember I started with twelve in early 2020, and still have ten (I lost one to ich, but I don't remember what happened to the other one). If you're looking for suggestions you might give them a try.

Here a picture of one I just pulled out of the tank on my desk (it's been in there for a while). This size is typical for the leaves from the live oak trees I'm familiar with.

There are a lot of species of oak, but I believe that is post oak.

I don't see any reason why you couldn't have cardinals and neons in the same tank. If you just want amano shrimp anyway, I wouldn't recommend them for eating algae. A nerite snail might be a better option. Whether or not neocaridinas do well in your tank will likely depend on the betta. Some kill everything in sight, and others won't. Assuming it's not bothering the neons, there's at least a chance it won't kill them.

I suspect someone confused amano shrimp with ghost shrimp, which can be aggressive. By the way, I'm not saying it doesn't happen, but I've never seen my amano shrimp eating algae.