High Alkalinity Question

[fftfk]

Hi -

My tank has been set up for about a year now. My in tank Alkalinity is consistently high. Today it tested at 12.5 dkh, calc is consistently 440-450, salinity is pretty steady at 1.025-26 range. I don't test magnesium too often but the last time I tested it was around 1300. Phosphate is .02 and nitrate is .00 (the tank is currently lightly stocked and I have too large a ball of cheato going.

The tank/sump entire setup is about 400-500 gallons. I do a 10% water change every 2 weeks using Instant Ocean Sea Salt (purple box). Water change water tested today resulted in 8.7 dkh and 440 calcium. Alk usually drops about .4 - .5 dkh after a water change.

I use a Deltec Twin Tech 2.1 calcium reactor. I have had it set to the lowest flow possible of 7 liters every 24 hours and my alk has stayed high. My understanding from research is that high alk is usually associated with low calcium. That does not seem to be the case with me. I bumped the calc reactor up to 10 liters every 24 2 water changes ago and it has not made a measurable difference. Any suggestions to get Alk under control? Bump up the reactor further?

Edit - two additional points of information. 1) The fish and corals I do have appear happy. All have been in the tank since December. 2). When originally set up my tank routinely tested 8.7 - 9.3 dkh. My tank unfortunately got a case of Uronema. Using the advice on humble.fish I treated my tank with H2O2 and believe I have substantially eradicated the uronema. However, the H2O2 treatments are when my alk spiked and has not come back down. (I would post a link directly to the site but am not sure it that is allowed here. My user name is the same so you should be able to find the info about the treatment plan, results, etc.)

Thanks.

John

 

[jda]

If you do not have a good amount of calcium and carbonate uptake in your tank, you likely will need to lower the alk in your salt mix before you add it to the tank.

I lower the alk in salt mix to around 7.0 - I use Instant Ocean too. I use muriatic acid for this, which is safe but it is an acid so you have to be smart in your handling and wait an extra day or two for the pH of the salt mix to rise again. I would almost NEVER recommend adding the acid to a tank with animals.

Most of the time, a 10% water change even at 12.0 dKh will not move the tank dKh much. However, if you are not using much carbonate in the tank, it will just stay high.

Let me know if you want to discuss decreasing the output of your Deltec, but it will require running it without a pH probe. IMO, not using a pH probe is a superior way to run, but plenty of people do not want to mess with this.

 

[fftfk]

I will look up the muriatic acid method...do you think it is a viable way to bring alk down permanently? I do not currently run a pH probe on my deltec so happy to hear about ways to decrease output. Thanks for your advice.

 

[jda]

Lower the bubble count and lower the alk from the CaRx effluent. Do you know want the effluent dKh is now?

Gallons * desired dKh drop * .123 is the number of MLs of muriatic to use.

 

[fftfk]

The Deltec CaRx is a saturation reactor. There are no bubble counters. It keeps a continuous giant bubble of CO2 in the reactor to ensure the liquid is saturated with CO2. I've never measured the effluent assume it's dkh is in the 12-13 range.

 

[jda]

I forgot about that. I don't know how to lower the output on that.