does too much salt kill ich?

[RowSonic]

I have a regal tang in my tank that had ich and i never seen him with ich again for 4 weeks. I broke my hydrometer about 4 weeks ago as well and i never measured my water's salinity until last night. MY salinity measured 1028 and my corals and my fishes and inverts never died or showed any stress in my tank. I am surprised my corals did not die actualy. I already corrected my tank's salinity last night.

Do you guys think that the high salinity in my tank killed the ich?
Everything in my tank has been so healthy for some rasons

[JJM]

I dont this extra salt would kill the ick,...if fact when some do quick freshwater baths with their fish , both the fish and the spores go through osmotic (sp?) shock, this shock stress's the fish and the ick , killing just the ich,...thats the theory if i remember it correctly......Your hydrometer could have been off ...

[ATJ]

Cryptocaryon has been shown to survive in salinities up to 40 ppt (e.g. the Red sea). A salinity of 40 ppt is equivalent to a specific gravity of 1.029-1.031. Your "higher" specific gravity would not have affected the parasites.

I must point out that a specific gravity of 1.028 is not really all that high and is much better for your organisms that one that is too low - e.g. less than 1.025. There is no reason to expect that 1.028 would have any adverse affect on any organisms in your tank. What is the specific gravity now, and how quickly did you lower it?

By the way, freshwater baths have been shown to be ineffective for the removal of trophonts from fish.

[dougstanula]

I thought that specific gravity should never go over 1.025, I am fairly new to the hobby. Is this a missinterpretation

[ATJ]

I have often seen that recommended, so it isn't your misinterpretation.

There's two main problems here:

1) Definition/understanding of "specific gravity"

2) Years of incorrect information from books and LFS.

Generally, specific gravity as used in the hobby is not all that accurate. This is because there are multiple standards that are used and so the same sample of water can have different specific gravities depending on the standard and device being used. Further, if the temperature of the sample is different from the standard, adjustments have to be made to the readings on the device to determine the actual specific gravity. For more information on specific gravity, see Specific Gravity (http://www.petsforum.com/personal/trevor-jones/specificgravity.html)

Salinity is a much more accurate measure and it is well defined.

The salinity of water around natural reefs ranges from 23.3 to 41.8 PSU (practical salinity units). The average salinity across reefs is around 35 PSU and most reefs have a salinity close to 35 PSU.

Depending on the standard used, a salinity of 35 PSU is equivalent to a specific gravity of anywhere from 1.024 (d25/4) and 1.028 (d4/4). In addition to salinity, my refractometer gives readings in specific gravity using d20/20 (density of sample at 20°C over density of pure water at 20°C) and so a salinity of 35 PSU has a specific gravity of 1.027.

The recommended range for specific gravity should be 1.025 to 1.027 (if you don't know the standard of the hydrometer).

Many books and LFS have been recommending a specific gravity much lower than that of normal seawater. Some of this is just based on ignorance, but some of it is based on the (flawed) theory that a lower specific gravity prevents parasites. While fish can survive in a lower specific gravity (or salinity) many invertebrates can not - especially echinoderms. Further, the salinity you'd have to go to to prevent parasites would result in the death of most invertebrates.

So again, the recommended range for specific gravity should be 1.025 to 1.027 (if you don't know the standard of the hydrometer).

I'm sorry if I have confused you, but unfortunately it is a confusing topic.

See also: What are Natural Reef Salinities and Temperatures…Really…and Does It Matter? (http://www.animalnetwork.com/fish2/aqfm/1997/nov/features/1/default.asp)

[RowSonic]

btw, hi ATJ!!! My tank seems ok now with salinity of 1023. THe I did some rockscaping and i noticed that most of my LR have black algae on one side. This black algae is quite slimy too. Any idea what it is? All my fish now is in a quarantine tank including a black stripe damselfish that i had to catch for at least over an hour.

[ATJ]

Hello Rowena,

A specific gravity of 1.023 is far too low for many invertebrates - especially echinoderms. And if you dropped it from 1.028 to 1.023 in a short period of time you may find that some may die. See the discussion above.

The black slimy alga is probably a cyanobacterium. It is not easy to eliminate. Good circulation in the tank may help.

[RowSonic]

is that the only way to eliminate the black alga?

[RowSonic]

by the way, this is out of the topic but my orange tree gorgonian is slowly fading its color from orange to white then the white will turn black. I thought its bec. of too much salt. IS there any links you know that will show me how to take care of gorgonians?

[ATJ]

Rowena,
There are many proposed methods for getting rid of cyanobacteria, some work for some and not for others. I recommend you do a search - probably in Reef Discussion - for "cyano" and see some of the proposed methods.

Unfortunately, "orange tree gorgonian" doesn't really narrow down the genus at all. Without knowing the genus it is not possible to know if it has zooxanthellae or not. Any chance you could get a photograph of it? It still may not provide a definitive ID, but it will help.

If it is without zooxanthellae, as the orange colour suggests, it is probably starving. Some gorgonians have zooxanthellae and this enables them to get energy from light. Many don't and must feed to meet all their energy and nutritional requirements.

[dougstanula]

so, what is your opinion on the ideal specific gravity for a reef/fish tank

[ATJ]

Originally posted by ATJ
The recommended range for specific gravity should be 1.025 to 1.027 (if you don't know the standard of the hydrometer).

[dougstanula]

thank you for all the advise, it seems to me that my local lfs was basically sending right down the wrong path