Auto Water change through skimmer questions

Here is an idea I had that I am considering pretty seriously. (as in I bought everything I need to do it tonight)

I am thinking of using my skimmer to automatically pull 2-3 gallons of skimmate out of my tank a day and have it drain directly outside. Then use my Apex with a conductivity module to tell my BRS 50ML a minute pump to add premixed saltwater to keep my salinity in check.

My current setup
- 210 Gallon display with apex controller.
- My auto top off is using a double redundant float switch and pulls directly off the ro/di filter (I travel a lot and wanted unlimited ro/di water, I know the risks inherent here)
- Reef Octopus 3000int Protein Skimmer

I'm thinking of leaving my current auto top off exactly as it is. Then adding the new conductivity module and BRS pump. I will set the conductivity module to pump the salt water for 30 min everytime it drops below 34ppt (1.025)

So.. my final questions are
- Is there any reason I shouldn't mix the salinity beyond 1.026 (allowing me to do say 40-50g of water change out of only a 30g container?) Using my auto top off and tank water to dilute the mix
- What's the most I would want salinity to swing over the course of a day?
- Is a constantly moving salinity of 1.025-.1026 a problem?
- How much salt would it take to move from 1.025 to 1.026 in a water volume of 180g+?

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Final plan.

Skimmer is plumbed to a 5gallon bucket with a bulkhead drilled at the 4 gallon mark or so that will dump any excess back into the sump. Giving me a hard 4gallon maximum before any else leaves and I have to make a decision (to remotely empty the bucket) The float switch at 2.5 gallons will warn me that the bucket is full and from there I can decide to activate the pump to dump the bucket to outside, or I can cut the skimmer off if I feel there is a problem (IE the bucket filled way faster than it should have)

The skimmer will be tuned to pull 2.5 or so gallons a day out and the salt pump will be programmed to dose 2.5 gallons a day back in (or the mathematical equivalent if I use water mixed to a higher salinity, which I plan too). The conductivity probe will only be used to monitor the salinity levels rather than as a decision maker. The ATO is unaffected by all this.

The biggest down side is I will need to tweak the salt pump each day to compensate for inconsistencies in the skimmer. But that's really not a big deal as we are talking small numbers on a big tank. This set up means that at most, I will have an additional 1.5 gallons of saltwater replaced with fresh water... Not a big deal at all on a system my size.

 

Sorry if this thread is a little all over the place, lol. I am getting really excited about the prospect of changing as much as 80g a month without causing any major swings in my tank parameters all while doing less work than it currently takes to change 20g.

 

If it were that easy and predictable, it would have been done already. I however do not trust salinity meters and other non-basic functions on a controller enough to rely on them while I am away. If you can make this happen and it is functional, delete this thread and sprint to your nearest patent office. You'll be wealthy

 

I'm pretty sure this has been done already is the thing. I seriously doubt this is all that original.

And conductivity is the most accurate form of salinity test.

The largest variable is the skimmer.. but it should be self rectifying so long as there is salt mix available. If the skimmer goes nuts and drops 5g one day, as long as the salt is there to keep up and the brs pump can dose fast enough, it shouldn't be a problem.

 

Interesting idea.
There are serious auto-water changers out there like Genesis Reef Systems - but I am curious to hear why you want to go the skimmer route? It this like a toilet flush so to speak?

matt

 

Mostly to minimize the equipment needed and thus an additional failure point. The beauty of this idea is that all I really had to add was a $90 BRS pump (they are on sale!) and then place my container for water change near my tank. I was going to get the conductivity probe anyway. I love data I can graph!

By using the skimmer I should get a relatively constant amount of water being pulled out of the system throughout each day. Also I feel like using a skimmer will get me the dirtiest part of the water. This means there is never any major amount of old water coming out or new water going in.. Steady as could be. And by dropping new water in the return section, I am always taking out different water than I am putting in!

I have heard of people doing water changes through wet skimming and it's always made sense to me for small water changes. I feel like this should just be the maximum of that idea.

 

You sound like a man that could pull this off..
I don't like adjusting a skimmer too much though - I like it to stay on the line - what kind of skimmer are you using for this? Many would not give me confidence to pull this off.
matt

 

Reef Octopus 3000INT.

Thanks for the vote of confidence! If you can help identify possible failure points, please do. The key to success here is going to be planning for what can go wrong before hand. Then setting up appropriate redundancies.

 

I will probably add something like this to help keep constant skimmate production

Reef Octopus Automatic Skimmer Neck Cleaner | CoralVue

 

i just addded the conductivity module and probe to my apex, the probe has been set up a month now and is keeping a good reading set in the salinity setting. recently seen my salt go up looked at my tanks sump and seen i forgot to fill the ato and my sump was low. its that accurate. only thing i find might be a problem is, it seems to take a bit of time for the reading to move its not instant.