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Having trouble with my salt...


Apr 8, 2005
Hi all, I've been lurking for some time now, and have finally decided to take the plunge and start up my first SW tank (in which I hope to eventually try a bimac). Apparently it'll be some time before I can try out an octo, as I can't even seem to get the salt to mix correctly. I'm using instant ocean salt in a 55 hex that's right at 74 degrees. I've got about 35 lbs of "homemade live rock" in the tank, but I think it's fully cured and shouldn't be causing a problem. For circulation I'm running a 170g/hr biofilter/powerhead, and when running air through the venturi, I can see bubbles circulating through the entire tank. The water is RO from my spectapure filter.

Every time I measure the salinity I come up with 1.023...so I mix in a little more salt, and instead of raising my levels, it just collects on the bottom of the tank. Right now I'm still below the amount the directions from instant ocean give...but as it's building up on the bottom of the tank, I'm assuming adding more is pointless? I'd like to run at 1.025, if I can get it that high.

Normally I'm pretty good at googling the answers to this kind of stuff, but I'm not having too much luck...hopefully this is just an embarrassingly simple newby mistake. Any hints?


Are you adding dry salt directly to the tank? This can affect how your salinity reads if you test it immediately after.

Aside from that, it is really bad to add salt directly to your tank. High concentrations that fall on animals, corals, etc. can burn them.
Sometimes you have to mix it pretty vigorously to get it all to dissolve, which is another reason to mix it outside the tank. I bring my DI water home in blue 7-gallon plastic water jugs. I measure the appropriate amount of salt into them and aerate each for a couple days to mix it before adding it to the tank. The salt instructions say that the chemical reactions take a while to happen.

Are you using the little plastic hydrometer with the semi-floating plastic indicator? Those things are notoriously bad. Use one to measure the specific gravity of di water and it won't tell you 0% salinity. Sometimes they get stuck and the indicator won't move, too. A lot of reef people suggest buying a refractometer for precision measurements. I think they cost ~$100? I still use the plastic thing, but I've done a couple of prepared solutions to get a rough idea of how inaccurate it is.

I'd be wary about the refractometer. Temp has an effect on the salinity reading they give and you have to suss out the differences and adjust accordingly!

I just have a separat 55gal rubbermaid barrel, it's only about $13, and i just put the RO water in there and the salt, and i leave it in there with my cheap powerhead on overnight

P.S.-if you're using the plastic hydrometer, make sure you're tapping all the bubbles off the arrow, that had me confused for awhile in the beginning :confused:
I agree with some of the previous comments that you shouldn't add salt directly to the tank. Sounds like yours is falling to the bottom and not even mixing in. Maybe someone has a better idea, but I think I'd try to siphon the extra salt out. You could increase the salinity a bit by letting some water evaporate and not topping off or by adding small quantities of water with a higher salinity over a period of days or weeks (a 10% water change with water at 1.025, for instance).

I bring home my RO/DI water in 5 gallon jugs and mix it in large salt buckets using a small powerhead to stir it up. Most of the time it mixes for a couple of days. If you mix it in this way, it should completely dissolve. Otherwise, you might try a different brand of aquarium salt.

Jean, some of the refractometers on the market now claim to adjust for temperature.


Thanks for all the replies...that was really fast...

I'm guilty of mixing my salt directly in the tank, but only because it was a fresh tank. I was aware it could be lethal to aquarium inhabitants, but since there were none, I figured it wasn't an issue. (apparently my first mistake :wink: )

I assumed it would take a while to mix in, but I've actually had the system running with filtration for several months. When the salt didn't all desolve right off the bat I figured it would take a few days, when a few days didn't cut it I put the whole project on hold. Now I'm ready to clean up my mess and get going...so I thought it would be a good idea to get some experienced views.

I do have a cheap $10 plastic hydrometer...but it seems to be taking accurate (or at least consistant) measurements. If I syphen out some of the water/salt currently in the tank and retop with RO water, my level drops. Right now it's at 1.022, but there is still a decent ammount of undesolved salt on the bottom. (ie, pretty much everything in the tank is covered with a "dusting" of it)

The package the hydrometer came in warned about the bubble thing...it still got me the first couple times though...those bubbles can be pretty darn small... :wink:

I guess the next step is to do as Nancy suggests and try to simply clean up the mess I've made and then slowly adjust it back to a correct level.

Out of curiosity, is there a general level of circulation one would recommend for an octo tank? If I mix my next batch of saltwater in a seperate container until it's fully disolved, and then add it to the tank, might it fall back out of solution? Maybe my 170gal/hr ph wasn't provideing enough turbulence to keep it mixed?

Thanks again for the help,

Nancy said:
Jean, some of the refractometers on the market now claim to adjust for temperature.


Really, haven't seen those......course stuff like that gets down under rather later than to other places :lol:

And I'd still like to test it! Our many 1000's of dollars worth of CTD (conductivity {AKA salinity}, temperature and depth) equipment still has to be calibrated!


i usually just mix my salt in a 5 gallon bucket until i can see the bottom clearly which takes about 5 minutes.
please tell me if im doing something wrong
Ya an octopus can excape through anything smaller than its beak so I would use a sump and some fome matting to block of the intake pipe and the outake pipe. use a realy powerful pump so you have a constant flow. good luck
And in answer to A Rabid Squid's salt question - salt doesn't fully dissolve in 5 minutes - you should allow a half day before using it. Put a small powerhead in the bucket or jug with for circulation.

Colin said:
hey jean, have a look on ebay i got a great refractometer for $30 shipped from the states which has Auto Temp adjust... works great, they have really came down in price as they were well over £100 jus 3 or 4 years ago here.

PS the $30US included shipping...

heres a UK advert for them http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=3212&item=4380888276&rd=1&ssPageName=WDVW i asume NZ has its own eBay?

Thanks Colin, will need to look into that!Would be a real boon to have one like that especially for our classes!

I just like to test everything.....guess that's why I went into science

hey cliff: i dont know if any 1 else has tried it yet but some some stores are now careying bottle sea water. i can say its 100% effective but ive been useing it 4 da past 2 months and my water parameters have been right on. plus its do reverse osmo whatever u call it so all the impuities have been removed and the water satarilized. plus the salinity is right about 1.025 so u dont have try adjusting b4 hand. if i can remember the brand ill let u know plus if any 1 has heard anything negative about this product please let me know. p.s. sorry about spellin and grammer. :lol: :-/ :cry: i aint no typeist.