toxic factor in ASW

[Luis A M]

Dear Randy,

I have found that new AW is toxic to adults and larvae of ornamental shrimps Lysmata and Stenopus.Even water changes of 20% produce acute toxicity distress and death.This toxicity seems species related as the water is completely harmless to other organisms,including the copepod A.tonsa,which is used frequently in toxicity bioassays.

The toxic factor does not disappears with simple aging,but it is lost in aquaria,possibly due to biological action.

EDTA has been pointed as the toxic agent,perhaps because it is the only compound alien to the inorganic natural salts mix.

Can I remove EDTA with activated carbon?If so,what kind,amount and time?.

Could the quality of ASW be affected by this treatment?.I imagine EDTA was put to keep some trace metals in solution.But if EDTA is consumed by bacteriae,this effect would be lost in aquaria,anyway.

Thanks for your assistance.So far I am raising larvae in used ASW but then WQ problems show.

[Randy Holmes-Farley]

Fresh ASW often contains ammonia, and that may do it.

How are you making the ASW? What salt? What source of water?

Some salt mixes do not contain EDTA. I'm not sure how well you can remove it once there. It may actually reduce toxicity due to metals.

[Luis A M]

I would be surprised if ammonia was the culprit.I am talking of acute toxic reactios,shrimps swim at high speed in great distress and die soon after.
While some people told me they had the same experience,this thing was never discussed in aquarium books,I don´t know why.
I mix the salt with tap water.I tried once diluting it in distilled water,but the effect was the same.I use Instant Ocean.It also happened with Red Sea and I suspect it will be the same with all brands.Which salt does not contain EDTA?,it will be interesting to try it!
I imagine bacteriae will destroy EDTA in the aquarium.Then instead of treating new ASW with carbon,I´d have to circulate it thru some sort of biological filter.

[Randy Holmes-Farley]

Which salt does not contain EDTA?,

I believe that Instant Ocean does not contain EDTA.

Do you have any access to natural seawater to see if that makes a difference for you?

[Luis A M]

I thought it did,will check.I think IO is based on the classic Sagedey-Kelly formula.
I have tried NSW and it was OK,as expected.But I can´t bring from the shore (400km)the volumes I´d need for raising shrimp larvae.
Will check if carbon removes the shrimp toxin (EDTA or whatever).If it doesn´t I¨ll have to run new ASW tru some kind of biofilter,as I know that water taken from a tank is not toxic

[Randy Holmes-Farley]

The claim is that in its current formulation, IO does not contain EDTA:

http://archive.reefcentral.com/forums/showthread.php?s=&postid=1258533#post1258533

[Luis A M]

Randy,thank you for the links.So the matter had been long discussed in the forum before.
Anyway,I´ve got the official statement from Aquarium Systems:
quote-Dr. Magnasco, Instant Ocean has no EDTA while Reef Crystals does contain a small concentration of it.unquote
Will keep searching the issue and post any update

[Randy Holmes-Farley]

Thanks, Luis Let us know if you find out the cause. :)

[Habib]

Luis:

Found this: http://www.reefs.org/library/article/magnasco_toonen.html

It sounds like it might be realted to your tapwater?

Is any chlorine added to your water?

[Luis A M]

Originally posted by Habib
Luis:

Found this: http://www.reefs.org/library/article/magnasco_toonen.html

It sounds like it might be realted to your tapwater?

Is any chlorine added to your water?

Habib,
Where you found that piece,at the antiques store?:lol:
While my tap water is chlorinated,most is lost at the building head tank and the remaining after circulating some time in the mixing vat.Never had a chlorine problem nor I use thiosulphate except when I need to use water right from the tap.In these notes,I tell that I tried asw made with distilled water and the toxic effect persisted.
I thought perhaps there was EDTA in IO in 1998 and was then removed,but they say there was no EDTA since at least 17 years.
Anyway,I think it´s time to remake my old experiments and see what pops out.Will keep you guys posted