Something is eating up my alkalinity

[Happyschneider]

Hi all,

I just started with sea water aquariums so I hope that some of you might be able to help me. My 180 liter tank (approx. 40 gallon, JUWEL VISION 180, approx 15 liters of stones (half LR and half dry LR) and sand) is running for a good 2,5 months now and is pretty much established. The values are more or less stable.

Temp 25 °C (+/- 1°)
salinity 34 ppt (refractometer)
pH 8.0 (+/- 0.2 depending on when I measure, using an electronic, freshly calibrated)
phosphates 0 ppm (milwaukee)
ammonia 0 ppm (salifert)
nitrates 5 ppm (salifert)
magnesium 1275 (salifert)
calcium 425 (salifert)

The only value that bothers me is the alkalinity. Ever since I started measuring it, it seems low (started at 6). I then got it back up to 7.5 using carbonate (fauna marine). Unfortunately, it seems not stable as it went back down. It is now back at 6.9. I am not sure what could use it up at the moment as I do not have any complicated corals.

I have a sand bed (shallow, approximately 3cm/1'), some hermite crabs, turbo snails and some nassarius. Almost no algae anymore but a lot of cyano growth. Is it possible that the cyanos are the things that are using up the alkalinity? There is also a ball of Caulerpa that is supposed to help me with the nutrient removal for the cycling period. I plan to remove it soon.

Corals in the system at the moment: sinularia flexibilis (1 week, 3 arms, approx 5 cm long, not very happy, the attachment seems to get brownish so probably need to cut that one off), Briareum sp (1 week, about 3 by 2 cm, happy, polyps already out and fluorescent green), Zoanthus sp (1 week, about 1 cm radius, happily opening up), easy to keep gorgonia (1 week, about 5 cm long, happy as far as I can tell). To my understanding none of these should use up the alkalinity like this and also they came into the system after I adjusted the alkalinity (original measurement and adjustment was done before I bought the corals).

Another lead might be that the tank stands in a cellar room where we are not very often. So there might not be much CO2 in the air. Also, the tank is covered by the JUWEL cover. Maybe this is a problem for CO2?

Appreciate any thoughts or input, thanks!


Michael

 

[Happyschneider]

MAybe an important point would be that I record the data in dKH and here is an overview of the past development (see attachment). The blue arrow indicates where I added the soft corals.

When testing the freshly made water for water exchange (made from RODI, 0 TDS and HW marinemix professional (German brand), I get a dKH of 8.0 I make approximately a weekly water change of 10% in order to remove as much cyanos as possible from the system).

Sorry for not including in the first post.

Michael

 

[serbusfish]

Almost everything uses your KH, corals use it to grow, coraline and other algae use it, when you do top offs it will lower KH, etc.

 

[Happyschneider]

Thank you! So you think I should just keep dosing it? I am just a little bit confused as calcium and magnesium are staying the same.

 

[ericarenee]

MAybe an important point would be that I record the data in dKH and here is an overview of the past development (see attachment). The blue arrow indicates where I added the soft corals.

When testing the freshly made water for water exchange (made from RODI, 0 TDS and HW marinemix professional (German brand), I get a dKH of 8.0 I make approximately a weekly water change of 10% in order to remove as much cyanos as possible from the system).

Sorry for not including in the first post.

Michael

if i do not add kalk to my ato water this happens to me.. I also dose a two part. But not enough..

But i Evaporate about 4 gallons a day on the near 350 gallon system...

 

[Happyschneider]

Interesting. So alkalinity is getting used up just like that... Obviously there is plenty in there using it up, I take that as a good sign. My issue is that I have so little evaporation that I hardly need to ATO. So I probably need to dose by hand...

Thanks, feeling better now. Just need to work out how much I need on a daily basis and will take it from there.

Michael

 

[serbusfish]

Interesting. So alkalinity is getting used up just like that... Obviously there is plenty in there using it up, I take that as a good sign. My issue is that I have so little evaporation that I hardly need to ATO. So I probably need to dose by hand...

Thanks, feeling better now. Just need to work out how much I need on a daily basis and will take it from there.

Michael

I have a very low amount of evaporation too as I have a lid on my tank so I dont need an ATO, I only have to top off with a litre of water every two days!

I use a powder kh buffer mixed in the top off water, but you can get a liquid kh buffer too, my friend uses one and its as simple as measuring it out and pouring it straight into the tank.

 

[Happyschneider]

That is an excellent tip. Currently, I am using a powder. So might look into the liquid option.