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Old 09/22/2015, 07:52 PM   #326
ttabbal
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I'd like to give this a go. I have a floor drain available, just need to connect up some tubing to drain the skimmer to it.

Am I correct that if I do this, then set the skimmer to run wet, and put 1.026 saltwater in the ATO, I'm going the right direction? I would also need to set up RODI for evaporation makeup, or set the ATO water to a lower salinity to compensate. Of course I will monitor salinity daily via refractometer and compensate for any swings.


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Old 09/22/2015, 08:10 PM   #327
Elliott
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Quote:
Originally Posted by ttabbal View Post
I'd like to give this a go. I have a floor drain available, just need to connect up some tubing to drain the skimmer to it.

Am I correct that if I do this, then set the skimmer to run wet, and put 1.026 saltwater in the ATO, I'm going the right direction? I would also need to set up RODI for evaporation makeup, or set the ATO water to a lower salinity to compensate. Of course I will monitor salinity daily via refractometer and compensate for any swings.
yes, as your skimmer removes skimmate, which has similar salinity to tank water, your ATO should replace that seawater loss with the same salinity seawater

your evaporative loss needs to be replaced with fresh water RO/DI, which can be estimated and periodically adjusted based on actual salinity measurements


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Old 09/23/2015, 11:06 AM   #328
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Originally Posted by ttabbal View Post
I'd like to give this a go. I have a floor drain available, just need to connect up some tubing to drain the skimmer to it.

Am I correct that if I do this, then set the skimmer to run wet, and put 1.026 saltwater in the ATO, I'm going the right direction? I would also need to set up RODI for evaporation makeup, or set the ATO water to a lower salinity to compensate. Of course I will monitor salinity daily via refractometer and compensate for any swings.
You will still experience evaporation which ordinarily would be replaced with fresh water since evaporation leaves the salt behind. Your ratio of water loss to evaporation versus water loss to skimming will dictate your make-up water target salinity. The art in a wet skimming setup is in finding just the right salinity in the make-up water to replace the salt you're skimming out, while not causing the tank salinity to climb over time. This will take careful monitoring and it will likely change seasonally.

Depending on how wet you decide to skim and how much evaporation you have, if either of these is really small compared to the other, and your inhabitants can tolerate the swing, you can get away with just monitoring it and adjusting it periodically. In time, if you just run a fresh water top off from a container and find you need to add about a cup of salt each week to the tank to make up what you're skimming out, you can just add that cup of salt to the week's container of fresh top off water and the result is a more stable system. Continue to monitor and adjust from there. If you top off direct from a plumbed RO/DI, it is a bit more challenging to automate. My first idea would be to slowly dose a saturated saltwater solution in small quantities with a peristaltic pump similar to dosing two-part. Some aquarium controllers may be able to dose it as salinity drops below a trigger point if you trust that sort of thing.



Last edited by swilliamson; 09/23/2015 at 11:23 AM.
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Old 09/28/2015, 04:55 AM   #329
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Using periodic wet skim water changes, some folks remarked at the aggrivation of resetting the skimmer back at the prior level for dry skimming. I have-first had experience that this can be a bit aggrivating at times. Once I set my skimmer to what I thought was appropriate and woke up the next morning with my skimmate reservoir full and water overflowing. I learned the hard way that it is never a good idea to set the skimmer without having time to observe it for a few hours.

Has anyone ever tried putting markings on gate valves to help reset the skimmer to prior, dry-skimming levels in order to reduce the guess-work? I am thinking of trying this. I doubt that it will be very precise, yet it should help.


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Old 10/09/2015, 01:28 PM   #330
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Using periodic wet skim water changes, some folks remarked at the aggrivation of resetting the skimmer back at the prior level for dry skimming. I have-first had experience that this can be a bit aggrivating at times. Once I set my skimmer to what I thought was appropriate and woke up the next morning with my skimmate reservoir full and water overflowing. I learned the hard way that it is never a good idea to set the skimmer without having time to observe it for a few hours.

Has anyone ever tried putting markings on gate valves to help reset the skimmer to prior, dry-skimming levels in order to reduce the guess-work? I am thinking of trying this. I doubt that it will be very precise, yet it should help.
Not sure if anyone has brought this up yet but a controllable DC needle wheel pump would be perfect for this as long as your base setting isn't already on the highest setting. When you want to wet skim you just bump up the pump speed and when you're done you drop it back down to your base setting.

Also, you could use your Apex to help maintain the salinity. Since the Apex is not terrific with the salinity accuracy you should be careful with this but it could keep it in the range better than manually checking it once a week. Basically, you would need 2 topoff containers, one for fresh saltwater and one for freshwater. You could just add the line in the code to your existing ATO code that if salinity is less than __ dose SW and if it is higher than __ dose FW.


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Old 10/09/2015, 04:36 PM   #331
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Agree getting skimmer reset after an over organic event is a PITA. It applies to wet skimming as well as dry....slightly off topic but you refer to marking a gate valve . I would love that but for my main drain control valve..I have tried every type I can find on the Australian market and cannot find one worth marking because the operating range on them is so narrow that my overflow chamber can be altered from empty to full by tapping on a wing of the ball valve. Surely a finely controlled wheel operated ball or gate valve can be had somewhere in PVC. I have tried blade valves from USA...looked good..still no controllability.
I have actually found a way to do this really well and that is by building a branch off the main drain with a small cheap ball valve in it say 1/2" ...and get the flow right with the main branch and then fine tune with the trim valve. It works really well if you can be bothered with the 30 mins plumbing.
So to get back on topic our standard ball valves/gate valves tend to operate in too small an area to be worth marking...they are really intended for full on full off use.


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Old 10/09/2015, 09:25 PM   #332
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Has anyone run two stage output gates to allow the option to run wet on demand?

The idea is to run dry most of the time, but trigger a second gate to partially close to initiate a wet "event" and flush for a few minutes before replenishing.


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Old 10/19/2015, 07:59 PM   #333
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Agree getting skimmer reset after an over organic event is a PITA. It applies to wet skimming as well as dry....slightly off topic but you refer to marking a gate valve . I would love that but for my main drain control valve..I have tried every type I can find on the Australian market and cannot find one worth marking because the operating range on them is so narrow that my overflow chamber can be altered from empty to full by tapping on a wing of the ball valve. Surely a finely controlled wheel operated ball or gate valve can be had somewhere in PVC. I have tried blade valves from USA...looked good..still no controllability.
I have actually found a way to do this really well and that is by building a branch off the main drain with a small cheap ball valve in it say 1/2" ...and get the flow right with the main branch and then fine tune with the trim valve. It works really well if you can be bothered with the 30 mins plumbing.
So to get back on topic our standard ball valves/gate valves tend to operate in too small an area to be worth marking...they are really intended for full on full off use.

I don't think there's a ball valve out there that will get you what you want. By their nature the flow resistance vs. valve angle on ball valves is steep and hard to control. Gate valves have a much longer control (rotation) per output (flow resistance). The downside to small changes is that they take a while to adjust. How much are you adjusting?
Using a gate and moving say 1/64 of a turn at a time, then waiting 10 minutes I would be surprised if you can't get the controllability you want.


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Old 05/15/2016, 11:40 PM   #334
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Interesting read.


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Old 05/16/2016, 11:45 AM   #335
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IMO it's the only way to roll


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Old 06/02/2016, 09:53 AM   #336
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Wow I just discovered this thread. I have been doing this for a few years now. I will have my skimmer overflowing the whole time I am siphoning the tank out and by the time I have taken out about 20 or so gallons of water my skimmer has filled up a 5 gallon bucket or 2 to add to the water change. Glad Im not the only one that does a water change with the skimmer LOL

I plan to wet skim soon so that I am doing almost continuous water changes through out the week. I will still do a water change a few times a month so I can siphon the bottom of the tank out. What I plan to do is have two 5 gallon buckets, one inside the other. I have the bottom bucket drilled in the bottom with a bulkhead and a pipe that goes out and up to about half the height of the bucket and then drains into my return section of the sump. I have the bucket filled about to the same height as the exit pipe with fresh saltwater. I then have a second 5 gallon bucket floating inside that bucket that my skimmers collection cup drains into. As the skimmate fills up the top 5 gallon bucket it forces the bottom 5 gallon bucket of fresh saltwater to drain into the sump keeping the water parameters and salinity in check.

Even if this works I will still have my skimmer overflowing during water changes to assist with the siphoning.


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Old 10/25/2016, 10:12 AM   #337
philipk2003
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Weekly 5 gallon water change

Here is a picture of how I do my 5 gallon wet skim change.

I elevate a 5 gallon bucket of salt water and drip it into my fuge with an air line.

I adjust my skimmer to remove water at about the same rate.

Takes two hours.

LOL... I can make 20 gallons of salt water, siphon out 20 gallons of old water, and refill in 1 hour.

However, this way, I do not turn any equipment off and my fishies don't get scared!


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Old 10/25/2016, 01:00 PM   #338
75mixedreef
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I've done that. It is time consuming but very efficient. The downside is that you cannot target certain areas to remove detritus or algae. Those factors together make it easier to just to a traditional water change after stirring everything up with a baster to the rocks. Once in a while I will do it for a gallon or two just to remove nutrients, not so much for adding back minerals.


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Old 04/26/2018, 09:25 AM   #339
gernby
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Bumping this old thread to see if anyone has improved this water change method using the new controllable DC skimmers. I just setup 2 Reef Octopus Elite 200-INT skimmers in my 2 systems, and believe they will be perfect for continuous automated water changes without any adjustments.

I found that when the skimmer is at its max setting, it begins wet-skimming whenever the water level in the sump is above ~7". Once the level in the sump drops to the magic level (seemingly determined by bio load), the skimmate becomes dry. If I slowly add water to the system, the skimmate becomes wet again, and the discharge rate increases to match the rate being added. I believe that I could use a dosing pump to provide a continuous feed of new water, and let the skimmer extract excess water at the same rate.

Obviously, safe-guards would be critical, especially for salinity and equipment failure (overflows). However, assuming an "ideal" implementation with no failure points, how certain can I be that continuous wet-skimming wouldn't actually degrade water quality in some way? Do skimmers ONLY remove unwanted "stuff", or might wet-skimming result in a lower concentration of beneficial "stuff"?


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Old 04/26/2018, 11:43 AM   #340
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How will you correct for evaporation? The system will drift towards the input water's salinity, but not without some lag. You would need to top off an estimated amount, slightly lower your replacement water salinity, or rely on salinity measurements to make corrections.


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Old 04/26/2018, 06:47 PM   #341
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How will you correct for evaporation? The system will drift towards the input water's salinity, but not without some lag. You would need to top off an estimated amount, slightly lower your replacement water salinity, or rely on salinity measurements to make corrections.
Who are you asking? If you are asking me in regards to using the skimmer as part of a continuous water change system, then I would say that I'd engineer the salinity control over time. I wouldn't want to rely on a salinity sensor alone to determine salinity, but a combination of many environmental inputs from other systems (HVAC, ventillator, humidity, etc.), I think it would be pretty straight forward to derive a feedback loop to dial in a safe algorithm for fresh water supplementation.


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Old 04/26/2018, 08:29 PM   #342
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Gernby, you are the one I was asking. I agree that salinity control by sensor is risky. I think you could get it close over time, I'm just pointing out that it needs to be accounted for, and am curious how other people think the problem is best solved.


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Old 04/27/2018, 12:16 PM   #343
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Gernby, you are the one I was asking. I agree that salinity control by sensor is risky. I think you could get it close over time, I'm just pointing out that it needs to be accounted for, and am curious how other people think the problem is best solved.
Well, I've been thinking about several strategies to control salinity, but won't decide which (if any) I would use until I observe it for a bit. I work from home, so I would monitor everything carefully until I gain some confidence in the solution.

However, here are some are a couple approaches I'm thinking about:
  • Mix the new water at a lower salinity than the tanks ... observe resulting tank salinity over time ... adjust mixture until an acceptable range is achieved.
  • Meter the discharge rate using an intermediate waste bucket with float switch and solenoid drain valve. Whenever the bucket fills to the float switch, flush the bucket. The number of "flushes" per unit of new water pumped would be an indicator of evaporation. The relationship between flushes per gallon of new water and the need for fresh water would be derived over time.

The controls and data collection would be an extension of my ongoing home automation / nerd project.


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Old 04/27/2018, 02:58 PM   #344
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I have used wet skim water changes for years. I feel it is a superior way to do water changes, removing more nasties/gallon than just siphoning. It's easy to do, also. Here is my technique:
I usually mix up 12-15 gallons of fresh saltwater (same Specific Gravity as tank water), unplug my pump from my RODI ATO reservoir and plug a pump that's in the fresh saltwater supply into the ATO switch system. The fresh SW pump then feeds into the last chamber of the sump via tubing that is secured above the level of water in the sump so you don't get any backwash siphoning happening. Then I just run the tubing from the drain in the cup of my skimmer into a 5 gallon bucket and adjust the skimmer until i get a steady drip/thin trickle running out of the skimmer into the 5 gallon bucket. As the water level in the tank drops from the wet skimming, the ATO switch activates and kicks on the pump in the fresh saltwater reservoir until the skimmed off volume is replaced. It takes about 2.5-3 hours to fill the 5 gallon bucket, which I just dump down the toilet when it gets full. This just keeps happening until the fresh SW has all been added to the tank and then I unhook everything, turn the skimmer back down to normal rate, plug the ATO RODI pump back into the ATO switch and I am good to go until the next water change.
This process usually takes about 8 hours, so I only do it when I'm able to be home all day. (I've done it for so many years that I now feel comfortable leaving the house for a few hours at a time, I just empty the 5 gal collection bucket right before I go).


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Old 04/27/2018, 03:22 PM   #345
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Because I only wet skim during the water change I find that I really don't have to worry about SG changes (8 hours of wet skimming per week doesn't seem to have much impact...I do always check the tank SG before mixing up the fresh SW and on the rare occasions that it has creeped up a little I just mix up a more dilute batch of fresh SW. Since it is being added a little at a time over 8 hours I don't feel the mis-matched SG is an issue.

Here is a post I made years ago when I first started the wet-skim water changes that show the favorable impact on my SPSs http://www.reefcentral.com/forums/sh...50&postcount=7


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Old 04/28/2018, 10:00 AM   #346
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fwiw

I still check into this thread every now and then- even though I've moved onward to few to absolutely no water changes. (I maintain Chaetodonts with scleractinians).
Those interested in this might want to research Triton (and related) methods.


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Old 04/29/2018, 06:23 PM   #347
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I just did a test water change in one of my systems using the skimmer to remove old water as I pumped in new water without any adjustments to the skimmer at all, and it worked even better than I expected! I simply pumped new water into the sump, and let the skimmer overflow into a bucket. It only took 21 minutes to do a 5 gallon water change, and the water level in my small sump is within a quarter inch of where it started. It actually stayed within about a half inch of where it started throughout the whole process.

My goal was to setup an automated continuous water change system, but now I think that it would be better to setup a simpler system that does a daily 0.5 - 1.0 gallon water change over a period of about 30 minutes (at an optimal time of day). With that approach, it would be much easier to control salinity, since the timing of the water change could be coordinated with the timing of the auto-top off to ensure a consistent end state.

Note that the skimmer was running with its pump speed at the highest level before, during, and after the water change. Also note that I replaced the flow adjustment valve on the skimmer outlet (rotating vertical gate valve) with a custom non-valved, fixed height "H-pipe", which yields a much more consistent / predictable discharge. You can see it in the video below.




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