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Salinity Question


Donya

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I have a potentially dumb question...where exactly is the lower end cutoff in salinity/specific gravity for water to be considered saltwater vs. brackish? There are a few salinity levels I'm trying to work out (doing snail studies, checking out salinity levels that Nerites prefer):

- Tidal system

- Saltwater estuary

- Reef

Are those all the same salinity range?

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Hi and sorry its taken me so long to get to this! Server and computer problems?anyway.

Brackish is considered to be any lower-salinity water; in reality it can range and can be almost full-strength seawater. Generally it is about in the range of 1.010 ppm. In nature, estuaries and bays are places where the rivers flow into the oceans, and at times the salinity ranges (even daily, such as when the tides are coming in and out) from almost fresh to almost seawater.

Nerites occur mostly in brackish water and proliferate there, though I personally have kept them in my saltwater tank. However, they probably would have lived longer in lower salinity.

So in answer to your question, brackish areas tend to be in the 1.010 range thoguh they can be slightly lower or higher. True specific gravity of ocean water is 1.026 ppm, and this is what water in the reefs and tidal systems would be. Animals in the estuaries are far more adaptable than animals on reefs. I often see invertebrates such as corals and anemones die in tanks where the salinity is off.

What sort of study are you doing? Nerites are interesting to me as well because I keep land hermit crabs, and a lot from Central and South America come in wearing different species of nerite shells, and as a result I have learned a lot about them. It is a challenge to find larger nerite shells when they grow as most nerites stay very small.

Anyway, hope this helps a bit!

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Ahhh...stuff's starting to make a lot of sense now, especially for the estuary salinity. Thanks for the info!

I'm looking into the salinity preference for Neritina reclivata. What got me started is that folks have trouble with them escaping in open-top freshwater tanks (myslef included), and mine were unhappy until I started raising the salinity. They are at 1.010sg right now, up from 0, and are loving it. I am suspicious that, with the exception of a few isolated populations of that species under very specific conditions, the species should not be considered freshwater. They may be able to survive in freshwater, but mine obviously wanted out of it. At 1.010, almost all "wandering" behavior has stopped, and their growth rate is amazing. They have grown 1/8" of shell in a little over one week, which is substantial given how small they are--and it also contradicts all the statements I've read about how slow-growing that species is. They are eating lots, mating, etc...generally they're happy campers. I'm waiting to see at what salinity the wandering behavior starts again, or if it even starts again as the salinity rises.

Also, it's interesting that Neritina reclivata is supposed to be able to reproduce succesfully and consistently in saltwater, but not freshwater (with very few exceptions--the veliger stage is evidently bypassed when in freshwater). That again suggests to me that the "freshwater Nerite" label often put on the species is an incorrect one (they are sold as "freshwater Nerites" with a clause that they won't breed in freshwater lol), and should probably only be only used for zebra nerites and other species that are known to breed consistently at low or no salinity. I have to wonder if a lot of the difficult care of Naritina reclivata relative to other species is due to keeping them in the wrong water conditions.

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  • 3 weeks later...
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They are at 1.019sg right now, they are beetling all over the place and eating like mad still. When do live rocks start to become usable? Can I put one in at the current salinity?

My filtration is going bananas on me with the salinity rise...finally got it to kick over to producing nitrate today, but my test kits keep showing nitrate for about 10 minutes and then it "disappears," so something fishy is going on (test kits are for fresh & salt water and work on another tank with no problem). I'd really like to go ala-live rock if I can, since it finishes the nitrate->NO2gas process. I'm trying to avoid water changes as much as possible, because I have veliger larvae and I don't want to wash them down the drain :krazy:

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Sorry its taken me so long to get back to this thread!! :o I found it so interesting I wanted to follow it. I too have read about the olive nerites not reproducing in FW (I was very close to ordering some last year for my plant tank). We recently got in some nerites at work in our reef tanks and I was noticing that some were hanging at or above the water line. I recently read an article about snails and they said that nerites often will crawl out of reef tanks and fry under the high intensity lighting. :( Well, that makes sense being that most of them are shore dwellers.

Live rock should be able to handle your lower salinity, however it may experience some die-off if it is coming from regular strength seawater. It is completely cured when you can put it up to your nose and it doesnt smell like disgusting sewage. It should just smell like the ocean. Are you curing it in a separate tank right now? How many pounds do you have? If you have a lot of of LR that should take care of your nitrate.

However what kind of filtration are you using on the tank? If you happen to be using something with a lot of biomedia (or a biowheel) you wont want to use that along with the LR. Basically that biomedia is creating nitrate which you dont want in your tank, and it will be outcompeting the LR for it. The LR should completely take care of all nitrates when the biofilter is functioning properly. I have about a pound per gallon (or more) of rock in my 30 gallon and have never had nitrate readings in the almost year that its been running.

Good luck with the babies and please post some pics when you can! :)

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Nerites do like to forage at the waterline and just above for food, so perhaps that's what gets the ones in saltwater with high intensity lighting. Mine don't seem to like bright light though, so I won't be doing a lot of lighting if I can avoid it.

I don't have any live rock right now and know nothing about curing...probably wouldn't have the space to do it even if I wanted to try. I was thinking of getting some from the pet store, maybe plopping it in a separate couple-gallon container and lowering the salinity gradually. The nerites right now are in a 5 gallon, because they're extreemly small and I didn't want to have something huge to manage for salinity adjustments. The filtration is one of the "wave making" pumps with a sponge stuck onto it basically. No other bio media, but since the filter is for a 20 gallon tank it keeps the ammonia at bay. It puts a turbo current in the tank, but they seem to be more active when their feelers are blowing all over the place than when they are in still water (at which point they go walking again...regardless of salinity).

So, if I put a piece of live rock in while I have the sponge thing going, the live rock will die? I could always take the sponge off and just have the pump be a pump with a mesh guard over it...but then I'd worry about it sucking up the veligers. A thinner sponge maybe? I tried using filter floss once but little strands got sucked up into the motor and it was a disaster.

I'll see if I can get some pics of the snailies...the veligers are way too tiney to get a pic of, with my cruddy camera anyway lol I'd have to catch them and have them under the microscope, which I havn't managed so far. Not sure if they will survive yet, that's part of the mystery I'm trying to unravel...what makes veligers turn into snails and grow up successfully.

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This is so interesting to me? last night after reading this post I went online reading about nerites and breeding. I had no idea what veligers were until then! :)

Most (good!) pet stores should cure their live rock before offering it for sale. We have a 125 gallon at work we use for curing the rock first. I think your idea of bringing it hoem and slowly lowering the salinity is a good one. After all, some people keep their SW fish in water as low as 1.020. I keep my tank at 1.025, so I had to acclimate everyone I brought home.

And since you just have a little sponge, that is not going to be a problem with the LR. If you had a huge wet dry filter or biowheels then it would be a problem, but it should be okay as is.

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Cool! There is a REALLY awsome store in my area that has cured live rock, I just have to see if they sell small enough pieces...I'd like it to fit in my tank :lol: the ones I've seen for sale online are gigantic. I'd also like to be able to afford it too :blink: good thing I saved some birthday money. Is temperature an issue for live rocks? My Nerites are running about 78-80F right now. I will have a hard time heating an acclimation bucket though...it might be around 70-72F. If I let the temperature go up graudally like for fish acclimation before adding will it be ok?

I found a bunch more veligers today in the hydrometer drip area that's magnified. They are strange little guys...I wish I'd found the eggs. I don't even know when they showed up. Here is a pic of the Nerites:

nerites1.jpg

They were doing some strange stuff today. A hair fell in the tupperware with them, and they followed it up and down repeatedly like ants on a pheremone (sp?) trail. They wern't trying to eat it, but I guess they thought it led somewhere lol. They also make "snail trains" and follow each other nose to tail around new environments.

Thanks for all the help on this, I really appreciate it!

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Not a problem. Thanks for posting the picture, that is so interesting!! Our store sells tons of live rock and you can even get "rubble"?all the small pieces that have broken off the large ones. Hopefully your store will have lots of different pieces to choose from.

The rock should be kept at around 78-80? but my guess is that it is pretty tough, being that most of it is shipped from Fiji and they just wrap it in damp newspaper to ship it. Of course, there is some die-off during that, but a lot of things still survive on it. I have had crabs, shrimp, sponges and even little starfish come in on my rock. :)

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I am so happy! The awsome LFS had live rocks/rubble kept in exactly 1.020sg, which is what the the Nerites were at this morning (evaporation I guess).

:nana

There are some cool polychete worms and stuff on the rocks. I know those are usually considered pests, but since I don't have any corals or whatever I think they are cool. There is a lot of purple stuff on the rocks along with some pale minty green stuff. I hope the nerites don't eat it all :crp I've attempted to attach a pic...first time I've tried without using photobucket so hopefully it'll work. I may go back and get more live rubble if I get more money saved up and move the Nerites into something bigger. Can't really see the minty green stuff...it's all over the middle piece.

post-4635-1133218094_thumb.jpg

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Yay, that looks great! Im sure it will be just fine. The pink stuff is coralline algae, which is a good, calcium based algae. The minty green is probably just another kind of algae. I dont think the nerites will be able to eat the coralline. Anyway Im glad you were able to find smaller pieces. :)

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Whoaaaaa!!! 4" giant tubifex-like thing just said hello from the tonga branch :yikes it just kept comming out lol actually I have yet to see the end...seems like I could have the blob and its extended blob family hiding in there.

Unfortunately as the snails are stirring up gunk on the bottom, the gunk is settling on the rocks and silting them up...pretty fast too. I have a feeling that's not a great thing to have happening, so I'm hoping maybe my 4" wormy friend(s?) might help out and dislodge stuff by wiggling around. *sigh* I have a lot to learn at this stuff. At least the snails are happy.

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Forgot to add in the last post: is there are a reason other than algal blooms why Phosphate is "bad" in marine systems? I use dicalcium phosphate for Ph-buffering and because when it is in a solid form, the snails eat it. I've seen no negative effects in freshwater, but is it toxic to marine beasties somehow? go0gle info is just telling me that "phosphate causes algae," but I need algae for Nerite food...

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