As long as its from a brackish tank they should be just fine. Switching salinity may cause some die off of beneficial bacteria. If you're worried about live plants then you'll have to reference many of the lists on the internet of suitable species. Good luck keeping live plants in a tank for Opae Ula though. Besides the already proven chaetomorpha. I have a feeling that you're worried about "bad" bacteria though. That I can't answer.
And good news! My shrimp from Mustafa showed up yesterday and after a bit of drip acclimation in they went. Last night they were all mostly clear. This morning before work they were starting to show a little blush.The ones that were out right after the lights came on anyway. When I got home from work they are pretty much all bright red and zooming around the tank in good numbers. There don't seem to have been any losses. They are, as Mustafa keeps reminding us, very hardy little bugs.
Now I just need to figure out how to get rid of the cyanobacteria outbreak that's cropped up. Last week I had a bit of a nitrite spike out of nowhere so I'm sure that has something to do with it (and the levels went away as quickly as they showed up. I'm wondering if the power went out for most of a day while I was at work and the lack of water flow through the filter bed killed off a good bit of my biological filter). That and apparently some tanks just have a cyano "phase" they have to go through. If it doesn't go away soon I'll just do a few days of darkness which seems to be the general remedy recommended by most. The weird thing is that its mainly focused on the sea fan in the tank. There is some on the inside walls of the uplift tube as well. No big deal, just annoying and hopefully not indicative of a larger issue.
Also worth noting is that the Marimo moss balls are doing fine at brackish salinity after an extended test.
Just get rid of the filter and you won't have any spikes of any sort ever again. As for the cyanobacteria, I would not recommend using darkness to fight it off. That will just release nutrients back into the water and most likely mess up the tank's biological balance. Try to collect as many "sheets" of algae as you can manually. I don't know if you ever got the brackish water snails from me, but those eat up that stuff slowly but surely over time. I never have any "bad" algae problems in my established tanks.
Let us know if the Marimo ball actually grows..and possibly "buds."
Let's just say that I have a mental block against removing mechanical filtration completely. I do have a couple 1.5 gallon tanks and I may just set up one without filtration to ease my mind a bit about making the transition. It's not that I don't trust you, I'm just rather set in my ways I guess.
And yes, I did get 20 of the snails from you and they are growing incredibly fast. Good to know that they'll eat the bacteria. Removing it by hand is going to be very difficult because of how its grown around the "branches" of the sea fan (I've already tried using a siphon and some scraping). And the fan is so big that removing the whole thing is going to result in a cloud of the stuff flying all over the tank if I remove it from the tiny hole at the top of the biorb. Yet another mark against the design. So for those keeping track, the biorb looks good, and that's about it. Its a pain in just about every other way. I knew that going into this situation already though.
Small update on the cyanobacteria. It's started going away slowly on its own. It's been steadily getting smaller and changing color from a strange, thick, deep reddish-brown to a sickly, light, semi-transparent greenish-brownish shade of ugly. Also today I've noticed that a handful of the shrimp have been hanging out on the clumps of bacteria and are picking at it whereas they pretty much ignored it before this. I'm wondering if it's somehow become more palatable the weaker it's become? Regardless I'd call all of this a good sign.
Great to "hear" that the cyanobacteria are retreating. That's usually what happens eventually as the tank matures. The snails and shrimp help immensely in the process (the snails mostly at night), and also make sure that the cyanobacteria don't come back.
As for mental blocks...as long as you know it's unreasonable to have such a block, there is always hope that you can get rid of it. Let me refresh your mind...I've had all of my tanks running filterless (and without water changes) for 7 years straight (and several years before that in NYC). Really, filters are *not* needed.
Well it seems that things keep progressing nicely. I was just spending some time watching the shrimp float around the tank and saw a baby brackish snail (definitely shaped differently than young nerite snails). Then I kept looking and saw three others. And that's just near the front of the tank, there could be many more.
I have seen quite a few snail eggs on the acrylic recently and they matched up with what nerite snail eggs look like from pictures. Some research seemed to reveal that most people don't have luck hatching nerites in captivity so I assumed they just wouldn't be viable. I can't seem to find pictures of the eggs of the brackish snails that Mustafa sells (Melanoides tuberculata, Tarebia granifera) so I don't know exactly which snails the eggs belong to. (I could just assume that they are the brackish snails but I'd rather know for sure). The eggs that I've noticed have either been hatching or dying or are being eaten as many are now hollow circles instead of opaque white ovals. See the attached picture with horrible focus - it's rather difficult to get a good shot of something so small on the glass with my phone/tablet. If a better closeup is needed I'll break out my real camera and I'll get a macro shot. There is also a snail in the picture (the leftmost red circle) for scale.
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I've seen Mustafa say in several places that the snails he sells don't lay eggs but are livebearing. I tired some searches to reference his posts but I didn't come up with anything. It's on here somewhere though.
Everything is chugging along just fine. The cyanobacteria has completely disappeared. The macro algae is growing like gangbusters. I am concerned that there is hair algae growing inside of the clump of macro. It doesn't seem to be causing a problem and the snails seem to like grazing around it so hopefully they'll keep it in check. Speaking of snails... Holy crap do they reproduce quickly and A LOT. I've lost count of how many there are and they are all different sizes. And they grow incredibly fast. I may end up transferring some to the bucket that holds my marimo moss ball experiment.
Regarding the marimo; the one in the tank that was doing well has started to show signs of deterioration. Spots of pale coloration are all over it. Meanwhile the balls in the bucket with an air stone are a nice dark green. The salinity is similar. I throw a little food in the bucket every once in a while to give them something to "eat". My only theory for the difference is that there is a much bigger water volume for the light to penetrate in the tank. (About 13-14 inches vs. 3 or 4 inches in the bucket. Distance from the light source itself is roughly the same.) I was turning them all periodically but now I'm just leaving the one in the tank where it sits see if I can get one side to green back up. For reference these are fairly large balls. About 1.5 - 2 inches in diameter.
I've also been experimenting with food for a little while too. I can't speak highly enough of the Repashy gel food. I'm using both "soilent green" and "shrimp souffle". It remains intact much longer than any of the pellet food I've tried so it can be removed much more easily if they haven't eaten it all in a reasonable amount of time. And they go NUTS when I toss a chunk in the water. It takes a little more preparation than just tossing in premade food but I think it may be worth it. I use a much smaller amount than the instructions suggest since they eat so little, but luckily you can freeze whatever is left over. The one down side is that your kitchen will smell like low tide for a little while since you need to "cook" it (microwave water and the powder or alternatively add boiling water to the powder). Small price to pay though IMO.
A quick shot of the rapidly multiplying snail babies.
The juvenile (total guess at size in relation to development) snails seem to like to congregate in the macroalgae. Anything much smaller, around 2mm and less, seem to stay in the lava rock gravel substrate and rarely venture more than an inch above it on the acrylic. I can't really tell whether they're eating hair algae or not but there's plenty of it in there for them to feast on. The macro does have areas that grow the regular old algae that we rely on to feed our shrimp so it's likely that's all they're after. The adult sizes seem to have a bit of trouble making their way through the macro but there are always at least a couple in the clump.
While on the subject of snails the two nerites are much less active (both sexually and as far as movement around the tank) now that the initial algae crop that developed while I was waiting for the tank to cycle is being kept in check by all the inhabitants. Not that there isn't anything to eat since the guts of the shrimp always look to be full of green stuff. That and the other snails are multiplying so readily so all seems well.
Thanks for the update! Glad that things are continuing to go well. The snails can actually eat decaying macroalgae and hair algae in addition to whatever microalgae may be growing on them. As long as something is soft enough, the snails can eat it. Your nerites have a clear competitive disadvantage when it comes to food. They ideally need a lot more food than both the brackish snails and shrimp, so them being less active may be just their way of conserving energy.
Best update yet? Two berried females, that I can count for sure anyway. There's so many swarming around its hard to get a read on it but I have seen two at the same time so that many for sure. I'm not expecting any young this early on but I'd call this a very good sign
And snails... Good god, the snails. I've started removing the easy to reach snails and moving them over into the bucket with the recovering macroalgae (its fully recovered at this point but I'm keeping it as a reserve amount in case anything happens to the macro in the main tank) and the other marimo moss ball in it. So far I've moved 42 and there are tons left. I'm trying to move the balance in favor of the shrimp as far as access to food algae goes. Lately the shrimp have taken to swimming more than they are stopping to graze so I'm assuming they're looking for food. I could be wrong but it can't hurt.
And now I've got 7 zoea floating around. The other day I was watching one of the mothers and her eggs looked odd, like they were falling off. I was certain that they were unviable. Now I'm starting to think they were about to hatch. I could be wrong, but either way, I'm on my way to a more crowded tank
As for the cyanobacteria, I would not recommend using darkness to fight it off. That will just release nutrients back into the water and most likely mess up the tank's biological balance. Try to collect as many "sheets" of algae as you can manually. I don't know if you ever got the brackish water snails from me, but those eat up that stuff slowly but surely over time. I never have any "bad" algae problems in my established tanks. 
