Invest in a refractometer as soon as you can. Hydrometers are quite inaccurate and can be off by as much or as little as 5-10 points at times (sometimes more sometimes less), and even 1 or 2 points can be detrimental to a system. It may show 1.025 but in reality be 1.015 or 1.035. Or again less. but you do get what you pay for with this tool.
I know thousands of people look to LiveAquaria to do a quick research of a fish prior to purchase. Yes they do sell fish in the US, but they have a good bio for each specimen.
http://www.liveaquaria.com/product/aquarium-fish-supplies.cfm?c=497+526
So check out the page for each snail and find some that do different jobs. Some like to stick to the rock, some prefer glass. Some eat detritus, other slime algae, others other type of algaes. They all have different jobs which is why it's important to get a variety. But be cautious some like to leave the tank and go for walk abouts. Some prefer colder ttemps and perish in our standard marine tank. some are quite large and knock stuff over all the time! I have 3 strawberry top hat snails that LOVE to knock all my un-glued corals over.
1. I currently have 3 Strawberry top hats. Their larger more pain in the butt snails, stick to glass and rock, do a similar job of the astreas, just prettier.
2. A bunch of Astreas (same as starry or pointy astreas) most people don't like these snails as they cant flip themselves over due to their small foot. I find these guys pretty hearty and one or 2 may fall off here or there, well then they weren't strong snails to begin with, and the circle of life takes place. They tend to stick to the glass, but I do find them on the rocks frequently enough. They prefer more turf algae and that film that builds on your glass initially.
3. A bunch of Ceriths (again many varieties) these guys chill out more on the rock. For some reason I cant keep these guys alive anymore. They like Diatoms, detritus.
4. I have 1 single Cowrie from 2 I introduced initially in my smaller tank over 2 years ago. These guys are just really pretty. I might see him once every 2 months or so, its like HEY hes still alive! Not sure what type he is, obviously a smaller species as hes only an inch and hasn't gotten any bigger. Really cool snail though. Stays hidden in the rock.
5. I have a dozen or 2 TONGA Nassarius snails. They live in the sand, eat detritus, and well their really cool looking. All you usually see is little sticks poking up from the sand, then you feed your tank, and its like an army of zombies rise from the dead! They make short work of ANY leftover fish food, dead fish, etc. So their quite useful. Mine have bred in tank and I have 3 or 4 little 4mm large ones trolling about. They generally come in just "Nassarius" and "Tonga Nassarius" The Tonga ones are twice the size, so about an inch or 2 depending how you measure.
That's whats in my tank.
I have tried Trochus because people claim they have a longer foot so can flip themselves over. But these things were ALWAYS upside down and could never manage to right themselves! Uggh, all ended up dying in a few days, stupid snails... useless....
These snails just don't reproduce and cause issues like in fresh water. Somebody makes a short meal of eggs very quickly.
Personally... Id try some Astreas, ceriths, and maybe 3 Nassarius. Start with 3 of each maybe?
A lot of other snails available just wouldn't have worked in my system due to temps or I didn't want some snail that could potentially be mean, or run out of my tank!
Your system can handle more but too many all at once will shock the system.
Its hard to say what other awesome snails you have available where you live. CITES to export fish/inverts/corals out of NZ/Australia is a pain in the butt at the best of times. But you guys have an epic natural selection so stores will have some great stuff.
