Tank Crash?

[Donya]

Test I've run so far:

1. Treated tap water at pH 8.6-8.8 + soduim bicarbonate = a stable pH of 8.4 in 1 hour
2. Distilled water at pH 8.8-9.0 + sodium bicarbonate = a stable pH of 8.4 in 1 hour
3. FW tank water at pH 7.2 + sodium bicarbonate = pH increase to around 7.8 (didn't add much sodium bicarb, just enough to see that the pH passed 7.5 and went up fast)
4. Solutions 1 and 2 at pH 8.4 with 1tbsp salt added = stable pH of 7.5 after several hours.

Everything right up until the last one on the list follows what I've seen in the past. I think there must be something wrong with that new box of salt I got. Instant Ocean is a big brand so I wouldn't suspect it to do that, but maybe I have a bad box...if that's possible. If it is indeed the salt, it was not a large contributor to the initial pH crash since the pH was fine that morning. However, I suspect it contributed greatly to my inability to get the pH up after the crash. It's still hovering around 7.7-7.8. I found a LFS that sells small jars of other salt brands for a couple bucks, so I think I'll get one of those and test it to see if I get a better result.

EDIT: the sg when I added the salt went up to about 1.020. I wish I'd measured how much water I was using but I forgot to write it down.

 

[SkiFletch]

very interesting indeed. wish I had an answer for you

 

[steelhealr]

A pH of 9 seems high for distilled. What kind of test kit are you using? Do you aerate when you mix your SW? SH

 

[Donya]

I'm using a combination of a digital pH meter (0.02 error margin) and aq. pharm. liquid pH test kits--both mid and high range for saltwater. So, it's 3 tests in all and with the exception of the mid range kit that periodically gives goofy results over 7.6, the results are consistent.

It's fairly aerated when I mix new tank water, both from mixing by hand and also I generally stick a bubbler in after the initial mix. For the pH tests I was doing, I couldn't use a bubbler but I checked with it unaerated and stirred by hand to the "whtie froth" level, and there was no significant pH difference (less than 0.1).

I got a small jar of red sea salt (red sea is the brand I guess?) and did the tap water/distilled water tests. As I was hoping, there was almost no pH change. What little pH change did occur was almost entirely undone with enough mixing. But, on the downside, the sodium bicarb is still being a pest. It does a sharp dip down to around 7.6, and I'm waiting to see if it will come back up. It seems to react a lot slower in saltwater than it does in fresh so I'm going to give it a few hours and see if it at least bounces back to 8.0. In theory, it should take the pH down from 9.0 and put it somewhere close to 8.

I'm still working on getting kH info...I can't find the instructions for my kit )

 

[Donya]

The baking soda is still being a pain. It worked in conjunction with raised calcium levels in a test jar, but then when I tried to apply it to the tank it did nothing. Ph goes back to 7.7-7.8 no matter what I do. I'm going to take a sample off and see if I can get it tested today and see if it matches the results I'm getting at home.

 

[Donya]

Still not being able to get the hardness measured. It's just a pile of live rock though so I have some time to sort things out. Just as an experiment I tried a small amount of a brand-name buffer. Darned if it didn't work immediately, on both salt brands. The main ingredient of the buffer is socium carbonate, rather than bicarbonate.

 

[SkiFletch]

Ok now THAT is wierd... Maybe the dying organism released some sort of chemical which destroys bicarb but not carb? Very very wierd chemistry you're seeing there


Edit: how old is your baking soda?

 

[Donya]

Brand new baking soda lol I thought maybe my previous box was old and that was the problem, but it wasn't since I went out and got 2 new boxes that did the same thing.

I just took 2 cups of tank water, 2 different containers...added sodium bicarbonate and the pH zapped down to 7.5 again (from 8.0, where the buffer fixed it to). Then, I took some home-made-from-the-oven sodium carbonate and added it to the second container, and the pH went right up to 9.2.

Sodium bicarbonate will undergo some reactions that lead to the release of CO2...which of course does bad stuff to pH. I'm wondering if that is part of what is going on. I will continue using the sodium carbonate and make sure the pH is stable. I probably got a really bad buffer-destroying chemical in there somehow from a nuking. As much tank water has been changed out as possible, so my hope is that it's back to being ok...I guess I won't really know until I put the first cleanup crew member in to test.

The diatom algae seems to think the tank is great now at any rate. The walls are turning brown before my eyes

 

[Donya]

pH leveled out at 7.95 as of this morning, which is a slight improvement. I'm hoping a little more work with a new water and sodium carbonate will make it stabilize closer to 8.2.

I take it the diatom growth is a sign of a recycle? I'm not picking up any ammonia or nitrite, and if there are nitrates it's too faint to tell. I also have some residule Caulerpa left in the tank...I'm wondering if I should take it out?

 

[SkiFletch]

Yeah, the diatoms are processing the nitrates from the mini cycle and feeding a bloom that way. A couple cleanup crew and you'll see them wiped out in no time If I were you I'd leave the culerpa for the time being as green plants are always good for an ecosystem

 

[Donya]

Is there any good way to know when it's safe for a cleanup crew to go in? (after the pH is stable that is)

EDIT: and after I make sure the ammonia/etc. is gone. It's just that the tank was so bad before I don't know if there is a sign that things are ok again...

 

[SkiFletch]

Umm, well, once your parameters read the following, I'd try it: ammonia 0, nitrite 0, nitrate 20 or less, pH 8-8.4 (stable), and an SG of 1.021-1.027 (again stable). Whether there's some kind of strange toxin in the tank is impossible to tell without adding some kind of life form... If I were you, I'd start out with a single hermit crab or single snail and keep an eye on it. If it lives for a couple days and eats, you're probably OK to add more crew until your diatoms are on the decline.

 

[Donya]

I think I've reached a stable pH. It's in the 8.18-8.20 range. I tested a cup of tank water with additional sodium carbonate and sodium bicarbonate and it seems fairly resistant to pH fluctuation. Finally!

 

[SkiFletch]

Nice, you're on your way now

 

[Donya]

Wooh! Stable tank and successful hermit test so far. And I actually have pretty white substrate showing now instead of brown fluffy gunk lol.

It looks like the problem I was suffering from with the sodium bicarbonate was...(insert dramatic music here)...a huge lack of sodium carbonate, which makes sense given that the water going into the mix was pretty soft. I discussed the situation with a chemist at my university and it's most likely that nearly all the NaHCO3 I was using was going right to CO2...which of course was no help with buffering.