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Salinty Issues

Jul 24, 2003
Got a couple of queries I hope to pick your brains on...

How much of an issue is it in doing water changes with different types of salt supplement i.e. if I go to different shops for my water and they use different saltwater :?:

Also why do we go for 1.026, I strive for this level and aim to keep it there but what is the lowest level an octo can tolerate (obviously without suffering!)

Im aware or am told starfish cannot handle salinity fluctuations and had one occasion were I could see a negative effect with a day of excessive evaporation, but how about an octo.

Hi Scouse,

In general, octopuses thrive in the salinity of natural seawater - sg of 1.026. That's why we recommend it. But there are variations even in seawater - the area near the shore when it rains, for instance. There are slight differences in parts of the ocean, too.

I would try for 1.026, but slightly lower would be OK (down to 1.024). I try not to go too much higher, maybe 1.0265.

Please tell me again how large your tank is - I'm surprised the sg is varying so much, even with evaporation. I keep a gallon of distilled water near the tank and top it off every night. Do you have a cover on your tank right now? That can make a big difference in evaporation.

There are slight differences between salt water mixes. There have been huge, heated discussions on various saltwater aquarium forums about which salt is best. I've also read of octopuses appearing "sick" when put in water from a different salt mix, so I try to be consistent and always use the same one (I use Kent Marine).

Cheers Nancy

Tank is about 44 uk gallons and when sump is connected there will be about another 15-20 gallons more (will have to measure for accurate)

Have been using Reef Crystals but am out of salt now will need to buy more or saltwater from LFS for sump.

For adding sump I am concerned if I dont use the same (RF) then the 2 clowns an starfish etc will have a bad reaction.

Wanna alternate to poss instant ocean or other.

I over estimated the variance of sg from evaporation. Using refractometer now for better results!

That incident when it changed a far whack was from a weekend when i wasnt there to top up. There is a cover on the tank somtimes (take off to run fan) but when sump is running will only evaporate from there.

Trying to sort an auto top off system to save hassle!!
Don't forget to occasionally chech the calibration on your refractometers and hydrometers. We were having way too much mortality in one aquarium room. Water parameters all looked good, mixing tank checked out. I just could not find the problem. Eventually we discovered that the refractometer being used in that room was off. We normally mix to 34 ppt and we were actually at 29. Now all refractometers are checked against one another and we have a scientific grade hydrometer to use as a final calibration.

auto top up will save you a lot of hassle... Look into the Aqua Medic range, I usd them on a large tank for a couple of years with no problem. I did end up gluing the sensor to the sump with silicone tho.

Ditto on the calibration of the refractometer. In fact all testing equipment should be calibrated on a regular basis. I do my digital pH meter fortnightly
nice one for the tip fellas!!

will look into aqua medic Colin.

Im seein it all for about 70quid second hand at mo but am wondering if it can be done a little cheaper through plumbers merchants, but thinkin oh is it worth the hassle to try an build it myself..prob not!!!..question questions!!! :lol:
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