Fish System Sabotage. pH 8.6, 24.2dKH. Help Would Be Welcome!

Magnifica · Jan 14, 2015

Hi all,

Sorry to disturb everyone, but I am currently having a bit of a crisis. A shady customer came into our shop last week who we believe has tampered with our fish only system which is 3,000 litres. Fish aren't looking the best now, and I have been trying to water change it down.

Prior to the persons visit.

pH 8.3
dKH 10.5
Calcium 410ppm
Magnesium 1250ppm
Salinity 1.024

Around a week later

pH 8.6
dKH 24
Calcium 400ppm
Magnesium 1220 ppm
Salinity 1.024

Skimmer has not gone crazy, carbon in the the system, and buffers are under lock and key by me. I haven't used any, so what could of caused this and what can I do?

Regards

Lee

UK_Pete · Jan 14, 2015

Thats about 750 grams of sodium carbonate added by my calculations (might be wrong though, see what the chief says!).

I recently used hydrochloric acid to reduce the alk in my system but on checking with Randy it turned out that it would cause a short term pH drop far greater than I expected. I guess adding mineral acids releases CO2 so until the CO2 is released back to the air (from a skimmer etc) the pH is low. In a fish only system though maybe this could be used carefully but don't do it without advise from Randy for sure! I suspect its too risky to try. Is a 50% or more water change practical?

beaslbob · Jan 14, 2015

Looks like someone dumped in some baking soda.
hope you get things under control with no (or at least minimum) losses

Randy Holmes-Farley · Jan 14, 2015

The pH is no concern, but the alk might be. I don't really know if fish respond much to alkalinity or not.

VERY SLOWLY adding some hydrochloric acid would be one way to bring the alk down, but it will temporarily drop pH a lot, which is why you want to go slow.

If you want to do that, we can come up with a recipe.

pirate2876 · Jan 14, 2015

dKH 24!! ouch!

Cory · Jan 14, 2015

I'd suspect the fish would die. Once I put a small piece of uncured cement in my tank thinking it wouldn't do any harm, well it did and all the fish died in a weeks time. I'm not sure if it was the dkh or the ph that did it.

If I was you I'd fill a large Rubbermaid with new saltwater and live rock and a skimmer plumbed into it and put all the fish or half in there until it's under control.

Magnifica · Jan 15, 2015

Hi,

Thank you all for your responses. How would I go about dosing hydrochloric acid?

UK_Pete · Jan 15, 2015

I was thinking about this last night, is it even possible to have such a high alk with that level of calcium, or might that be too supersaturated? Is there any milkyness to the water? If that level of supersaturation is not possible then your test could be bad. Just seems unlikely that someone would be able to dump almost a kg of sodium carbonate into the system and get it to dissolve without anyone noticing. And if someone wanted to sabotage your system wouldent there be easier things to do it with than alk? Unless it was a mistake by a staff member perhaps.

Anyway assuming the alk really is that high and you wanted to try hydrochloric acid, obviously wait for Randy to work out the dosages, but you would probably want to get a dosing pump ready, and get some hydrochloric acid, maybe you can get that through good quality sources that would be pure enough for a reef tank. The idea would I think be to drip it in really slowly to the intake to the skimmer probably (so the CO2 could be ejected off to the air to some degree by the skimmer). You would probably want to set the dosing pump to dose a couple of seconds every few minutes and watch the pH of the skimmer effluent with a probe.

If the above 750 grams of sodium carbonate is about right (not sure about that) then I think you would want about 1.2 litres of 20% hydrochloric acid (6M hydrochloric acid) but thats just a guide for how much to order, definitely wait for Randy to work out how much because my chemistry knowledge is only quite basic and I could be wildly off. Another name for hydrochloric acid is muratic acid btw. It is available as concrete cleaner but that might have impurities in it, but its quite a common acid so try your regular suppliers. It is cheap at least. I think it has to be hydrochloric acid btw because organic acids like vinegar will add far too much carbon, and of the mineral acids, nitric would add heaps of nitrate, phosphoric acid would add phosphate etc. Hydrochloric acid only adds chloride which is always high in seawater anyway so a small increase would not affect things.

IIRC when I asked Randy about this a week or two ago he worked out that a 1 dkh drop in alk would result in an immediate roughly 1 pH unit drop, so you could only drop the alk slowly with this method, depending on the power of your skimmer I think (not sure about this though), because the skimmer will then raise the pH again over minutes to hours by releasing the CO2 freed in the water by the addition of the acid.

UK_Pete · Jan 15, 2015

Magnifica didn't realise you were in the UK. Where are you roughly?

7hogwarts · Jan 15, 2015

I had a similar situation with alk. The fish were fine. but I lost most of my corals. I dealt with it by doing water change, water change, water change. 30 -50 percent everyday for about 14 days.
However, the alk spike caused my sand bed to turn into a brick. I couldn't get the "brick" to go back into being a sandbed. Now it is covered with coralline algae and has many corals growing on it.

Randy Holmes-Farley · Jan 15, 2015

Not sure exactly what is sold in the UK for hydrochloric acid, but muriatic acid in the US is typically about 34% HCl by weight. Some brands now are much more dilute (saving them money) and claim it is low fumes (it is).

Full strength muriatic acid (~34%) from a hardware store is about negative 34,000 dKH. So about 0.1 mL per gallon will drop alkalinity by about 1 dKh. It will also drop pH a lot, but only temporarily.

I'd drop the alk by 1 dKH and check the pH an hour later, then repeat if you want.

Be careful with it as it will burn you and especially don't get it in your eyes.

UK_Pete · Jan 15, 2015

I have bought hydrochloric acid concrete cleaner here in the past but it had a green tint which I assume meant iron impurities.

Randy, when you say a gallon, do you mean a 3.8 litre gallon or a 4.5 litre one? I have always assumed whenever someone from the US says a gallon they mean a 3.8 litre one but recently saw a US reefer using the 4.5 litre conversion when talking about tank volumes so I'm not sure whether both factors are used at different times.

Also is it right that CO2 is freed in normal ASW when acid is added?

Randy Holmes-Farley · Jan 15, 2015

A US gallon, of course.

3.8 liters.

Yes, a lot of CO₂ is made as the bicarbonate is converted into CO₂:

HCO₃^- + H⁺ --> H₂O + CO₂

UK_Pete · Jan 15, 2015

Ah right thanks on both counts!

Magnifica · Jan 16, 2015

Hi all,

No there is no cloud or was no cloud to the system. In theory if someone came in just before closing and did it, we would have never noticed.

We have opted for water changing it out, thanks to a purchase of large RO unit that fills 1 litre in about 15 seconds.

Thanks once again.