Contaminated Water?

[Ferris]

Hi all,

This may get a little lengthy so please bear with me.

The problem is this - my neighbour has a reef tank setup, which he has had for around 12 months now. He uses RO water with an ROman system. Every so often when he does a water change, 1 of the 10 litre buckets of fresh RO water will become cloudy when the salt and buffer is added to the water.

When i say cloudy - i mean really murky and milky looking. You can't see the bottom of the bucket - nowhere near. The water in each case always appears crystal clear until the salt and buffer is added.

Both the salt and buffer are from the same batch he has been using now for months so i think this can be ruled out as he changes 60 litres at a time and this only ever affects 1 bucket - the problem is that it's not always the 1st bucket of RO water that has the problem, which would make some sense as it could be the RO system not flushing properly. This doesn't happen every water change and sometimes can be the 3rd or 4th bucket in the process.

I'm no scientist but this would appear to be some sort of chemical reaction between something already in the water and the salt and/or buffer.

The RO system filters have been completely replaced 5 weeks ago and the system is flushed once a week before doing the water change. He thought replacing the filters had fixed the problem until it occured again yesterday.

I also have a marine tank and use an RO system and have never had this problem so i also think the mains water supply can be ruled out.

I think he will need to get a sample of this cloudy water professionally tested to get an answer but i just wanted to make this post on the off chance that someone has experienced something similar or has any ideas as to what the problem could be.

This isn't affecting his tank by the way as obviously none of this water goes anywhere near it and all his water stats are fine. (slightly high nitrates but then he is a little overstocked )

Any idea's/suggestions very welcome and much appreciated

F

 

[JaminRat]

Odd. I assume he is using the same same bucket not lots of different buckets. Most salt companies recommend to mix and heat for 24 hours prior to use does the water clear after this time?

Cloudyness sounds like the calc or alk comming out of suspension may just be adding buffer before the levels have stabalised in the mix.

 

[Miss Wiggle]

wierd, to rule it out i'd try a different brand/batch of salt and a brand new bucket

 

[Ferris]

Thanks for the replies guys - He's tried different brands of salt and buffer (mine ) and it made no difference and remember 95% of the time - this doesn't happen. He goes through the same process with every bucket - 10 litres of RO water - add the relevant amount of salt and buffer and then heat the water. When this cloudyness occurs - it happens as soon as the salt/buffer has been added and never clears - in fact it gradually gets worse.

He has 6 10litre buckets and it's not always the same bucket - the buckets are thouroughly rinsed etc before commencing water changes too.

It's a real mystery and i think he will have to get the water tested somehow to get a definitive answer but you never know - someone may have had something similar.

 

[SkiFletch]

Ah this one's easy, I dont even have to read the entire post .

1 of the 10 litre buckets of fresh RO water will become cloudy when the salt and buffer is added to the water.

"Buffer" is just bicarbonate/carbonate (usually baking or washing soda). In a natural seawater solution (which a salt mix tries to replicate), carbonate/bicarbonate are present in the water, the total of both is known as the alkalinity. In NSW, alkalinity is allready high and near saturation. When alkalinity reaches saturation in NSW or becomes supersaturated, it becomes highly reactive with calcium, especially if calcium is below its own saturation point. So when you have a situation with high alkalinity and moderate calcium, a reaction between the two forms a salt known as calcium carbonate. In NSW solutions whose pH is inherently alkaline (above 7.8 in this case), calcium carbonate is not soluble. It will not dissolve and will make the water appear cloudy, and in time stick to surfaces as a white crust.

When you add buffer to a solution with salt mix in it, you are likely coming right to that saturation/supersaturation point of alkalinity and creating just this case. There are really two answers to the problem. First, add less buffer. While most salt mixes are SLIGHTLY defficient in alkalinity, they are not anywhere near dangerously defficient in it. Second, aerate with an airstone to increase CO2 in the water, thus dropping the pH, and making calcium carbonate more soluble. This solution works well if you OD alkalinity in a display tank and get cloudiness there, yet isn't really the best in a salt mixing bucket.

Hope that made sense.

And a quick edit: If your friend is having trouble with alkalinity in his system, it'd be wise to look into a two-part additive to dose it, a calcium reactor, or a kalkwasser reactor to help keep alkalinity high there without messing with buffering water changes.

 

[Ferris]

Very very useful Ski - thanks.

Interestingly the cloudy water in question finally settled last night and left what looks like calcium deposits at the bottom of the bucket, which ties in with your post so i think we're getting somewhere.

 

[SkiFletch]

Anytime Ferris. I simplified that a lot. If you want the full brain wracking details, check out this article by Randy Holmes-Farley