Hyposalinity

[ahullsb]

I'll let you guys argue over whether it's harmful or not. The only question that actually seems relevant in this thread is whether or not it is NECESSARY to hypo fish longer than 6 weeks. I don't want to introduce my fish back into a tank that still has ich present. But I don't want to keep a 55 gallon rubbermaid garbage can in my dining room one minute longer than I have too either!

[jacmyoung]

But you will not get the answer unless the argument is settled

[ahullsb]

True. Has anyone hypo'd for 6 weeks and not gotten rid of ich?

[Amphiprion]

Originally posted by ahullsb
I'll let you guys argue over whether it's harmful or not. The only question that actually seems relevant in this thread is whether or not it is NECESSARY to hypo fish longer than 6 weeks. I don't want to introduce my fish back into a tank that still has ich present. But I don't want to keep a 55 gallon rubbermaid garbage can in my dining room one minute longer than I have too either!

I don't want to argue at all--I just want more evidence in either direction. I suppose someone should start a new thread to keep this one more on topic, though.

[TerryB]

Can't say that I have seen studies for keeping reef fish in hypo for years at a time. However, there is some evidence that the seas were once much less saline than they are now (about a third). That would support the contention that many saltwater species actually had to adapt to higher salinity over a great period of time as apposed to just tolerating lower salinities. Still haven't seen anything to support the kidney damage idea for marine teleost fish.

Here are a couple of links to check out.

http://advancedaquarist.com/issues/nov2004/short.htm

http://www.advancedaquarist.com/2006/3/aafeature1

The two paragraphs below are from the article that I wrote (see the second link).

"Contrary to the commonly held belief that a salinity lower than natural seawater is stressful to marine teleost fish (bony reef fish), reducing the gradient (difference in salinity) between the internal fluids of fish and the surrounding ambient water alleviates water and ion disturbance (Wedemeyer, 1996. Carneiro &Urbinati, 2001). Fish held in water that is close to isotonic (the salinity of the surrounding ambient water is close to matching the internal fluids of the fish) have increased stress resistance (Lim et. al, 2000). These fish also display a significantly lower mortality rate at 7 days post shipment."

"Although studies indicate that at least some species of marine teleost fish grow faster in a salinity of 14ppt than at 35ppt (natural seawater) (Lambert, Dutil, and Munro, 1994), I do not suggest maintaining hyposaline conditions indefinitely. Do not subject marine invertebrates, sharks, rayfish, "live rock," or "live sand" to hyposaline conditions."

TerryB

[ahullsb]

I see this thread going in two different directions also. I've also heard arguments both ways on the effects of hypo on fish. I'm still wondering what people think about ich staying in your tank for 10 or more weeks.

[TerryB]

Normally it isn't necessary to treat with hypo longer than three weeks to a month. This is provided that the salinity is constantly maintained at the correct level. Generally, I treat for 30 days, but nothing really wrong with going a bit longer just to be safe. If you are still seeing ich a month into treatment then there is a good chance that you are not measuring the salinity correctly, using an inaccurate device, or have misidentified the problem. However, there are a couple of hypo resistant strains of Cryptocaryon irritans in Taiwan so it is possible that one of them could end up in your tank.

I rarely suggest copper anymore. The transfer method works, but it is more stressful to the fish than hypo unless you are skilled at minimizing the stress of transfer and handling. If I use the transfer method then I combine it with hypo.

TerryB

[richard snyder]

I've got to agree with TerryB
I've kept my large FO tank in Hypo salinity for 5 months with no adverse efects. My 5year old queen angel,black and white spotted puffer,2ft - 3year old snowflake eel, show sized desjardini tang, how sized yellow tang and 5year old cat shark are still alive and eating like pirahnnas. I've read of a Fish store keeping a few angels in constant hypo for a few years without any ill effects. I'm sure there are some past threads onRC concerning this

[TerryB]

It is unlikely that ich tomonts will survive and remain infective up to ten weeks. True, if the water temperature is low enough it will extend the life cycle, but this would not be at reef-type temperatures. The second factor is that the longer that this parasite remains in the tomont stage (reproductive stage off of the fish) the less ability it has to infect fish or be viable once the tomont hatches.

My opinion stated above is based on past studies. However, this may change as C.I. has shown the ability to adapt to wider geographical ranges, temperatures and even salinities in some cases in recent years.

TerryB

[Amphiprion]

Originally posted by TerryB
Can't say that I have seen studies for keeping reef fish in hypo for years at a time. However, there is some evidence that the seas were once much less saline than they are now (about a third). That would support the contention that many saltwater species actually had to adapt to higher salinity over a great period of time as apposed to just tolerating lower salinities. Still haven't seen anything to support the kidney damage idea for marine teleost fish.
TerryB

All that does affirm the effectiveness of treatment in the short term but only on certain systems. Yes, most evidence does point to seas that were much less saline and that today's marine fish have adapted to that level. It is because of those adaptations that they are more suited to the environment they are in. That is why I don't think long term exposure is a good idea--as you agreed with yourself. I am a full proponent of hyposalinity treatments for the commonly prescribed amount of time (3-6 weeks, sometime longer if deemed necessary by resistant strains). The only other thing that I noticed is that of the fish studied, none of them are reef fish. Most of them are either freshwater (different physiological mechanisms) or frequently go between marine and brackish water (usually adapted well to low(er) salinity to begin with). Many of the fish we keep are strongly and exclusively associated with invertebrates. That is just the thing on evidence--I haven't seen enough evidence to prove or disprove that there is renal damage with long term hyposalinity treatment in marine fish.

*Edit* Thank you for taking the time to list your citations, Terry B. There were several in there that I had never seen before. I am all for getting more info.

[TerryB]

A little more info about studies using hyposalinity on marine fish.

Effects of salinity on the ionic balance and growth of juvenile turbot
F. Gaumet, G. Boeuf, A. Severe, A. Le Roux, N. Mayer-Gostan.

Abstract
The effects of salinity changes (27, 19 and 10¡ë) on seawater-adapted juvenile turbot were studied on their plasma osmolarity and ion concentrations, on oxygen consumption, on gill Na+,K+-ATPase activity after 3 months and on growth parameters. All plasma concentrations (except chloride) were unchanged, suggesting that fish were well adapted to their environment. Oxygen consumption was significantly decreased in the 19 and 10¡ë groups, where fish weighed significantly more 105 days after transfer than fish maintained in sea water. These results, and the fact that apparent food conversion rates were lower in a diluted environment, suggest that on a long term schedule growth conditions could be improved by adaptation to brackish waters (salinities between 10 and 19¡ë). The effects of transfer from sea water to 27, 19, 10 and 5¡ë were also followed during the first 3 weeks. With salinity 10¡ë a steady state was reached on day 21 with all plasma values within the same range. The significant differences observed in osmolarity, plasma ion concentrations and Na+,K+-ATPase activity 3 weeks after transfer of juveniles to 5¡ë salinity, compared with transfers in higher salinities, suggest that there is a threshold of acclimation of turbot to a hypotonic environment.

Tolerance of seahorse Hippocampus kuda (Bleeker) juveniles to various salinities

G. V. Hilomen-Garcia,
R. Delos Reyes and
C. M. H. Garcia

Southeast Asian Fisheries Development Center, Aquaculture Department, Iloilo, Philippines

Summary
In line with current conservation efforts, some success in the captive breeding of the seahorse Hippocampus kuda (Teleostei: Syngnathidae) has been achieved. To evaluate the salinity tolerance of these hatchery-bred juveniles, 9-week-old H. kuda were transferred without prior acclimatization from ambient full strength seawater (32¨C33 ppt) to salinities ranging from freshwater to 85 ppt. Survival, growth, and total body water content were determined after 4 and 18 days of exposure. Juvenile H. kuda are able to survive in dilute seawater (15 ppt) for at least 18 days without any compromise in growth (both wet and dry body weight), survival, and total body water. Fish abruptly transferred to freshwater succumbed within 4¨C24 h, while survival of 5 ppt-reared fish decreased to ca. 65% in 18 days. Although 10 ppt-reared seahorses had growth and survival comparable with the control (30 ppt seawater), total body water was significantly elevated indicating reduced adaptability. The upper limit of H. kuda salinity tolerance was 50 ppt. Fish reared at salinities ¡�55 ppt succumbed within 24 h. Like several other marine teleosts, growth and survival of juvenile H. kuda tended to peak in diluted seawater salinities of 15 and 20 ppt. These results indicate the possibility of growing hatchery-bred H. kuda in brackishwater environments.


Cheers,
Terry B

[HDAlien]

I used that exact same article to cure my CB of ich. It worked perfectly! Just follow the directions exactly.