Constantly Battling Against A Low Ph

[dilbert]

Hi all,

I got today the fasTest alkalinity test from Aquarium Systems right, I didn't read properly their table. It's meq/L and not degrees of hardness.

So all my three alkalinity test show over the last month 12, 13, and 16.8 degrees of hardness. 16.8 degrees is 6 meq/L and 5 meq/L should the maximum level of alkalinity in a tank. Once I measured even with that fasTest test kit 7 meq/L.

Despite that, I lose every day 0.1 to 0.2 ph and I am creeping always around a ph of 8.1 maximum.

At the beginning I added the 3 recommended caps of Seachem's Liquid Marine Buffer to the tank, generally at night before going to sleep.

Then, I used also Seachem's Kalkwasser powder to prepare a bottle with hard stuff that I used for the daily top-up to compensate evaporated water that is about half a liter or a pint.

Even with that I got never higher than ph 8.10 when it has fallen to 7.90. I use a 30-GBP handheld digital ph meter that I calibrate every week and sometimes I also use test strips.

Is there anything I can do to stop this daily ph drop?

My guess is it comes from the air in the room as PVC double-glazed windows are tightly shut and central heating is running most of the time.

Calcium should be around 450 mg/L with this unprecise Sera test I got. Maybe it's even higher with that kalkwasser I pour in every night. Magnesium I haven't measured so far.

 

[SkiFletch]

Hummm, did you have this problem during spring/summer/fall when you had windows to the house open? Or were you not testing then? Also, have you tested some freshly mixed saltwater for hardness and pH?

Edit: It is very possible that environmental CO2 is your pH problem. Remember, lower pH is ok so long as its stable. I struggle keeping my pH over 8.0 in the winter and dead heat of summer when the windows are closed

 

[dilbert]

I've set up the tank two month ago and bought the first snail and shrimp only a month ago.

Also, summers are quite cool here so that even in August central heating is often running at least during night. This summer we had only a handful days where it was warmer than 70 deg F.

The ph of freshly prepared saltwater is 8.15. Salted RO water from my LFS is about the same as he makes his RO water from the same tapwater as me (same Yorkshire Waters area). Normally, I use his RO water for preparing saltwater for the marine tank.

The tapwater has a ph of 7.4 and once I measured KH with a test strip and it was 6 deg KH.

I don't know if measuring the alkalinity of the freshly prepared saltwater makes sense as in the tank it depends also on the substrate, crushed corals or aragonite sand, or not?

I got a very thin sandbed of 1/3 to 1/2 inch which is not in favour of alkalinity, I guess.

But at least those three different test kits show values from 12 to 16.8 deg KH, so I don't dare to increase alkalinity with a Seachem product.

 

[SkiFletch]

So you're tank pH is 7.9-8.1 and the pH of freshly mixed water is 8.14? Sounds just fine to me. All values being slightly low would indicate the presence of ambient CO2, which is not surprising in a mostly closed up house. Long story short, unless your pH starts swinging wildly, I would not be overly concerned.

As for the KH of freshly mixed water, the reason I asked is perhaps your particular batch of salt has very high KH, thus leading to increased levels in your tank water. If your salt mix is high, it's no wonder the tank water is high. Make sense?

Finally, are you topping up with RO or tap?

 

[Lynden]

I could perhaps recommend a refugium with 24 hour lighting, preferably. The extra photosynthesis should help lower the CO2 to a level below what simple gas exchange at the surface could do. Though I agree that a pH of 7.9 to 8.1 is perfectly fine.

 

[dilbert]

I am topping up normally with DI or RO water, despite our tapwater has only a measurable amount of phosphate (1 mg/L) and none of nitrate or even ammonia or nitrite.

Well the refugium with 24h-lighting is also somewhat cost-intensive, but I'll think about it.

If not, I'll probably stay with topping up with kalkwasser (RO or DI water + Seachem's powder).

 

[SkiFletch]

Remember, most refugia only have moderate lighting, typically in the 18-36 watt range for your average sized reef. Doing some math with say 36watts: 36watts times 24 hours times 30 days gives you about 26000 watt hours, otherwise konwn as 26 kilowatt hours which is the unit of measure your electric company charges you. So multiply 26 times your cost per kilowatt hour and you've got how much it costs per month to run the light. In my neck of the woods, electricity is $0.10/KWhr, thus the light costs me a whopping $2.60 per month to run.