CaRx purge frequency vs. pH and alk levels...

[RSnodgrass]

Different take on the CO2 purge...

I finally got on board with doing more purges with my Aquarium Engineering stacked reactor. I started at once a week then a few times a week, and now daily.

Few observations that need testing to verify but it seems very plausible...

1) How often you purge, at a minimum level, is most likely related to your run time ratio (on/off). I run 17 sec on 330 sec off cycle.

2) I run my purge right as lights hit full intensity (initially because that's when I'm around to make sure it's working). I strongly suspect my effluent dkh concentration drops throughout the day and night (post purge). I'm going to start it a couple hours earlier now though to ramp up the effluent concentration before full lights.

3) The side benefits of this relationship/timing (I suspect) are that my pH is less negatively impacted at night and my alk production is at it's peak when it's needed and it's lowest potency at night when not needed = super stable Alk levels in the display.

Granted this is all probably nit picky and purging more then once a day at my demand would likely reduce my on/off runtime ratio.

Could less run time could also reduce the impact on my pH or does the more acidic concentration counter act that entirely... dunno.

Thoughts?

 

[P-Dub]

Interesting. I say this because I have never purged my CaRx. Frankly, I don't even know what you would be purging or why it would be necessary. Care to enlighten me?

 

[RSnodgrass]

I should have added that this is an auto reactor so there is not a constant input of fresh CO2 into the chamber as with a standard reactor.

Instead it adds CO2 until an internal float trips leaving a pocket of CO2 at the top. That pocket will naturally be absorbed and be partially replaced with other gasses. Then CO2 at some point is added again to make up for what was absorbed and not replaced by inert gases. As you can imagine this reduces the purity in the CO2 air pocket and raises the internal pH. Thereby reducing the effluent dkh concentration.

Some like Avast use a monster air pocket significantly reducing the need to purge.

The CO2 bubble eliminates that variable of tuning (mostly), the on/off cycle benefits (IMO but not shared by everyone) are explained next.

Currently I'm at 252 cycles/day of adding effluent to the tank vs. a drip at ~86,000 cycles/day. A 0.05 sec difference in drip timing can yield a cumulative change of 4,114 drips per day or 4.7%.