Alk and pH staying low

[Starkrost]

Hi all. My tank is doing “okay” but I think it good be much better. Everything’s surviving but nothing really seems to be thriving. What do you suggest?

Here are the current parameters:
temp 76.3
salinity 1.026
pH 7.61
ammonia 0.001
nitrite 0
nitrate 40
alk 7.0
phos 0
mag 1500
calcium 420

The tank is 4 months old and started with Life rock and live sand. It’s 13.5 gal with approx 10lbs of rock and an average of 1.5 inches of sand bed. I do an approx 25% WC every week.

My pH drops this low at night and comes up to around 7.8 during the day. The windows are open all day and night. This is a Fluval Evo AIO so there’s no separate fuge and no skimmer. I’m using filter floss, chemipure blue, and ceramic rings for filtration.

Livestock includes:
2 small clowns
pistol shrimp
peppermint shrimp
yellow watchman goby
blue tuxedo urchin
5 Trochus snails
1 margarita snail
1 rock flower anemone
some palys/zoas
1 lepto
2 candy canes
xenia
tiny GSP
2 heads of frogspawn
Yuma
2 plate chalices
1 favia
2 cyphastrea
minimal coralline
a little green bubble algae
a little GHA
reddish-brown stuff on maybe 1/10th of the sand

Thanks!!!

 

[dragon99]

How are you measuring pH? That seems suspiciously low if you have open windows.

One suggestion for raising it would be to make sure you have good surface agitation. If you can move/point a powerhead so that it gets a more turbulent water surface that may help with gas exchange.

PO4 measuring 0 worries me just a little, but given your NO3 is pretty high I assume there is plenty of PO4 input and it's just getting bound or used in the tank.

 

[Starkrost]

Measuring pH with both API and Seneye and it’s consistent between the two. 40 is the lowest I’ve been able to get my nitrates in a long time. I feed maybe a dozen of the smallest pellets once/day and I watch the clowns each eat 3-4 and the pistol shrimp eat 3-4.

 

[Starkrost]

Oh! And the wave maker is pointed towards the surface so I get pretty good surface turbulance.

 

[Randy Holmes-Farley Verified Community Expert]

I think that pH is unlikely to be accurate with open windows, but in addition to recalibrating, you can try the aeration test here:

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/


The Aeration Test

Some of the possible causes of low pH listed above require an effort to diagnose. Problems 3 and 4 are quite common, and here is a way to distinguish them. Remove a cup of tank water and measure its pH. Then aerate it for an hour with an airstone using outside air. Its pH should rise if it is unusually low for the measured alkalinity (Figure 2). Then repeat the same experiment on a new cup of water using inside air. If its pH also rises, then the aquarium’s pH will rise simply with more aeration because it is only the aquarium that contains excess carbon dioxide. If the pH does not rise in the cup (or rises very little) when aerating with indoor air, then that air likely contains excess CO2, and more aeration with that same air will not solve the low pH problem (although aeration with fresher air should). Be careful implementing this test if the outside aeration test results in a large temperature change (more than 5°C or 10°F), because such changes alone impact pH measurements.

 

[Starkrost]

That is an amazing and informative article and superbly written! I will try the aeration test today. Thank you very, very much.

 

[Starkrost]

Ok, here are the results:

Fresh outside air:
Starting pH: 8.0 (API) (Seneye Reading 7.74)
Ending pH: approx 8.3 (API)

Room air:
Starting pH: 8.0 (API) (Seneye Reading 7.74)
Ending pH: 8.2 (API)

So it appears the room air is not an issue. But I was quite surprised by the disparity between the API test and the Seneye. Which one do I believe? It’s a fairly new slide in the Seneye but the temperature reading is off by 3-4 degrees also with my Hygger thermostat. Should I set the trim on the Seneye to match the API test?

Thank you again!

 

[Randy Holmes-Farley Verified Community Expert]

I generally do not have confidence in the Seneye. Too many reported issues. Not a fan of pH kits either.

In general, though, the tank would benefit from more aeration.

 

[Starkrost]

Ibiersknly do not have confidence in the Seneye. Too many reported issues. Not a fan of pH kits either.

In general, though, the tank would benefit from more aeration.

Thank you

 

[blasterman]

A nitrate level of 40 is maybe arguable in a 10 year old tank packed with mature coral. Its not justifiable in a 4 month old small tank.

I guarantee there isn't a molecule of free phosphate with those params, and that's part of the problem

40ppm of nitrate with your aggressive water changes and just a couple of clowns doesnt compute. Either your test kit is goofy or you are feeding those kids whopper meals. Worth trying a second party for nitrate testing. If tank is indeed running at 40ppm nitrate something is wrong.

What's also happening is the big water changes are elevating alk and then it crashes back to 7. Even soft corals don't care for that. It's a young tank though and not much you can do.

Try pointing a house fan at the tank and see if it bumps pH up a bit. If the surface of the tank has agitation and your room is getting outside air this might be the missing link. Some all in ones have terrible gas exchange properties because they are sealed uo. Another reason I'm not a fan.

I would take a ball of cheato in that back filter or a skimmer anyday. That would really solve multiple problems.