Help!! Low pH & Dead Fish

[Drew1600]

Greetings all,

I have a Fluval Evo 13.5, set with a few pounds of live sand and about 14lbs of dry rock.
Tank has been cycled for about a month, so added a clownfish 2 weeks ago. Have a fully functioning CUC including 3 Mexican Turbo's, 2 Emerald Crabs, 2 Scarlett Hermits. Noticed some white stringy poo so treated with PraziPro. After seemingly clearing up, added a watchman goby 2 days ago.
Wake up this morning and they have both passed away. CUC all seemingly fine. Is it likely the clowns internal parasites were not cured, and a possible ammonia spike caused the goby to pass as well? Or other issues entirely?
Did a water change followed by testing. Also been having low pH problems, dosing with Seachem Marine Buffer but now KH too high. Do not believe it is a CO2 problem.
Parameters:
pH: 7.6 (added 2 teaspoons of baking soda)
KH: 13 (high KH, low pH?)
Calcium: 460
Nitrate: 0
Nitrite: 0
Ammonia: 0 (post-water change)
Salinity: 35

I am at a complete loss of understanding, any help at all would be greatly appreciated. Thank you so much for your time and consideration.

 

[lazycouch]

low ph can be due to co2/oxygen levels - put an airstone in there for 24 hours and check if it rises. if it does then thats your issue and your fish probably suffocated !

 

[Biglew11]

High dkh and low ph sounds like co2 problems or not enough air exchange. Alot of new reefers chase ph with dosing stuff. This is bad practice. The high dKH was caused by adding baking soda. Adding the buffer to raise ph likely has your salinity artificially at 35ppt as buffers contain contain other salts that will get read as salinity. Imo buffers shouldn't be sold at all.
Do have tank covered or open top? What kind of circulation do you have in the tank to facilitate gas exchange.

 

[chipmunkofdoom2]

pH: 7.6 (added 2 teaspoons of baking soda)
KH: 13 (high KH, low pH?)

Baking soda lowers pH, it doesn't raise it. Baking soda also raises alkalinity. In general, there are no additives that raise pH that don't also raise alkalinity. High alkalinity is totally possible with low pH. Having said that, I doubt the low pH killed the animals. The low pH is probably a result of the deaths.

Take a cup of water outside and aerate it for about 10 minutes. Then, measure pH. If pH is not at least 8.1 - 8.2, your pH measurement device is faulty.

 

[Drew1600]

Thank you all for the quick replys! I will immediately add airstone and see if it helps. Does it need to be in main tank or is back chamber sufficient? I do run the stock Fluval lid/light

 

[Drew1600]

For circulation/exchange I run a mini protien skimmer and the Cascade 500 as an additional filter, plus stock filtration

 

[Drew1600]

Should I add a 250gph circulation pump as well or will it be too much for this size tank? I would like to keep corals in the future but it seemed like a lot for my old clown