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Oasisreefling

Continuous water changes and salinity in pico

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My tank is 5 gallons and it's drilled and I intend to add a P trap in the wall for it so if I use a standpipe I can pump SW on a timer instead of RO on a switch. Seems simple enough. 

I'm wanting to figure out my top up/change over water salinity based on my current salinity and required make up water. A calculator would be nice but I'm wondering if any of you do this, even on larger tanks.

I am realizing with a 5 gallon even my make up water must be the exact temp when adding 1 pint. So less severe and more frequent changes seem like the answer considering I intended to do weekly 100% changes and keep SPS so might as well ditch the ATO.

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Oof, this is tough. It's going to depend on your evaporation rate, that's the big problem.
I'd say if you want to do this without having to watch salinity super carefully, it has to be more complex.

1. Have a water level sensor at the level you want to keep it.
2. Have a pump that can be turned on for 'x' seconds that removes water to the drain, or do this with a solenoid so it regulates that drilled egress.
3. Have a pump that can add RODI
4. Have a pump that can add new saltwater.

Every day, turn on the RO pump until the water level sensor is wet (replacing evap)
Then open the solenoid/turn on waste pump for "x" seconds to drain the amount you want (you could set this right a second water level sensor down lower, but time should be a reasonable system). Say 10 seconds drains a pint (hypothetical goal).
Then open the saltwater pump until the water level sensor is wet again


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Evaporation is driven by three things: the temperature difference between the water and the surrounding air, air movement over the water, and the relative humidity of the air moving over the water.  Since the temperatures and humidity can change hour to hour and day and day to day, you're unlikely to be able to dynamically adjust the salinity of the replacement water to avoid having a traditional ATO in combination with a reservoir of saltwater that's at the correct salinity.

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Posted (edited)

I wonder how off I'll be with a single res setup, I would expect an amount of fluctuation where manual adjustments would be necessary every few days. With seasonal changes. So far my top ups have been very consistent daily. It is a small surface area in the most stable room of the house with no air vents near.

I suppose my goal here would be less salinity control and more overall parameter stability. Less chance of shock on Saturdays for a little Tuesday Thursday SG check. Algebra should help figure out what I need to add fresh or SW wise.

But there's no reason I couldn't use two reservoirs. Buckets stack. Im on a free.99 run what ya brung budget so lets see...

How about this. A float switch feeding a DPST relay at 120v with Terminal A feeding an RODI pump and terminal B feeding a SW pump. The relay is switched by 120v from my aquacontroller jr which also powers the valve. The valve is on a recycle timer X seconds ON max off.

So the ACJr kicks on for a minute, the valve opens and the sump section drains. The float switch engages the SW pump instead of the RODI pump. The valve closes after X seconds, the sump section fills until the float valve shuts off the pump and after one minute total the ACJr turns it all off before the recycle timer can complete its cycle and turn the valve on again. In the off state the float switch goes back to controlling RODI.

Just a quick trip to my shed, a couple beers, a rainy weekend, annnndddd....

 

 

Edited by Oasisreefling

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9 hours ago, Oasisreefling said:

My tank is 5 gallons and it's drilled and I intend to add a P trap in the wall for it so if I use a standpipe I can pump SW on a timer instead of RO on a switch. Seems simple enough. 

I'm wanting to figure out my top up/change over water salinity based on my current salinity and required make up water. A calculator would be nice but I'm wondering if any of you do this, even on larger tanks.

I am realizing with a 5 gallon even my make up water must be the exact temp when adding 1 pint. So less severe and more frequent changes seem like the answer considering I intended to do weekly 100% changes and keep SPS so might as well ditch the ATO.

Interesting!

If you could run your ATO first to account for topoff, then do you saltwater topoff, that would account for evaporation.

Certainly tricky since the saltwater relies on overflow, which will be higher than the ATO.

A peristaltic water change would probably be best.  Pump out X mls, pump in X mls.

Keep us posted!

 

 

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7 hours ago, Oasisreefling said:

I wonder how off I'll be with a single res setup, I would expect an amount of fluctuation where manual adjustments would be necessary every few days. With seasonal changes. So far my top ups have been very consistent daily. It is a small surface area in the most stable room of the house with no air vents near.

I suppose my goal here would be less salinity control and more overall parameter stability. Less chance of shock on Saturdays for a little Tuesday Thursday SG check. Algebra should help figure out what I need to add fresh or SW wise.

But there's no reason I couldn't use two reservoirs. Buckets stack. Im on a free.99 run what ya brung budget so lets see...

How about this. A float switch feeding a DPST relay at 120v with Terminal A feeding an RODI pump and terminal B feeding a SW pump. The relay is switched by 120v from my aquacontroller jr which also powers the valve. The valve is on a recycle timer X seconds ON max off.

So the ACJr kicks on for a minute, the valve opens and the sump section drains. The float switch engages the SW pump instead of the RODI pump. The valve closes after X seconds, the sump section fills until the float valve shuts off the pump and after one minute total the ACJr turns it all off before the recycle timer can complete its cycle and turn the valve on again. In the off state the float switch goes back to controlling RODI.

Just a quick trip to my shed, a couple beers, a rainy weekend, annnndddd....

 

 

Ah yes, I did something similar many years ago back when I used to actually do water changes.

https://www.reef2reef.com/threads/apex-automatic-water-change-without-dos.216530/

Basically drain down the sump to a float switch, fill it back up with saltwater.  Of course, disable ATO when all of this is going.  Lot's of redundant floats and checks...

It worked well, I changed out 700 gallons at 5 gallons per change.

 

 

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9 hours ago, Oasisreefling said:

I wonder how off I'll be with a single res setup, I would expect an amount of fluctuation where manual adjustments would be necessary every few days. With seasonal changes. So far my top ups have been very consistent daily. It is a small surface area in the most stable room of the house with no air vents near.

I suppose my goal here would be less salinity control and more overall parameter stability. Less chance of shock on Saturdays for a little Tuesday Thursday SG check. Algebra should help figure out what I need to add fresh or SW wise.

But there's no reason I couldn't use two reservoirs. Buckets stack. Im on a free.99 run what ya brung budget so lets see...

How about this. A float switch feeding a DPST relay at 120v with Terminal A feeding an RODI pump and terminal B feeding a SW pump. The relay is switched by 120v from my aquacontroller jr which also powers the valve. The valve is on a recycle timer X seconds ON max off.

So the ACJr kicks on for a minute, the valve opens and the sump section drains. The float switch engages the SW pump instead of the RODI pump. The valve closes after X seconds, the sump section fills until the float valve shuts off the pump and after one minute total the ACJr turns it all off before the recycle timer can complete its cycle and turn the valve on again. In the off state the float switch goes back to controlling RODI.

Just a quick trip to my shed, a couple beers, a rainy weekend, annnndddd....

 

 

I could see this working but I would want so many failsafes and redundancies in it before I would trust it that it would likely get too complicated... but that's just me 😁  If @TheClark has done it then that would be a good template - he knows his tech/automation.

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ok, one thing to maybe consider here...5 g is so small, you could probably cheat the system here...

Say it's really 5g of water, and you can run a dosing pump or other slow and reliable pump from a relatively large vessel of saltwater.

We want our reef at 1.026, but anything from 1.023 to 1.028 is probably fine, right?

So fill up that reef with 1.026, fill the vessel with 1.024, and once the cycle is done, start doing slow but large water changes daily, just push water in and let the excess fall out to your p trap.

yes, evaporation will happen, and yes, the salinity in the tank will average higher than the 1.024 you're putting in. Yes, the salinity in the tank won't be perfectly consistent as evaporation rates change, but that should be a pretty slow event. evaporation should mostly be happening when the house is warm, so you could focus the water changes during the hours your heater is mostly likely to run (and the room is warmest).

If you change a gallon a day, of maybe 5g a week, but do it as maybe a half or whole pint per hour for 8-16 hours in the day, water temp should be trivial. It will reach an equilibrium, and with this 20% daily change, I bet it's no big deal. Say one day's evaporation would raise salinity from 1.026 to 1.030

 

Quick math says if you lose 2 cups a day to evaporation (Seems high to me), and have your new water at 1.024 with 20% daily changes, your tank will trend to 1.0267. If in that same setup, your evaporation is only 4 oz/day, you'd trend toward 1.0246, which is a tad low, but probably okay for most things. If I'm vaguely right that evap will stay between a half cup and two cups per day, then you might be just fine, at least if you keep less sensitive species

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I like this idea, feels like the simplest and most likely to succeed.   Just PUSH 1 gallon a day of fresh salt water into the tank and let the excess simply overflow.  Salinity movements would be small and gradual.

 

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1 hour ago, albertareef said:

I could see this working but I would want so many failsafes and redundancies in it before I would trust it that it would likely get too complicated... but that's just me 😁  If @TheClark has done it then that would be a good template - he knows his tech/automation.

The weak point is definitely the float switch in this chain. My relays are 20amp 600v rated lol.

31 minutes ago, Burningbaal said:

ok, one thing to maybe consider here...5 g is so small, you could probably cheat the system here...

Say it's really 5g of water, and you can run a dosing pump or other slow and reliable pump from a relatively large vessel of saltwater.

We want our reef at 1.026, but anything from 1.023 to 1.028 is probably fine, right?

So fill up that reef with 1.026, fill the vessel with 1.024, and once the cycle is done, start doing slow but large water changes daily, just push water in and let the excess fall out to your p trap.

yes, evaporation will happen, and yes, the salinity in the tank will average higher than the 1.024 you're putting in. Yes, the salinity in the tank won't be perfectly consistent as evaporation rates change, but that should be a pretty slow event. evaporation should mostly be happening when the house is warm, so you could focus the water changes during the hours your heater is mostly likely to run (and the room is warmest).

If you change a gallon a day, of maybe 5g a week, but do it as maybe a half or whole pint per hour for 8-16 hours in the day, water temp should be trivial. It will reach an equilibrium, and with this 20% daily change, I bet it's no big deal. Say one day's evaporation would raise salinity from 1.026 to 1.030

 

Quick math says if you lose 2 cups a day to evaporation (Seems high to me), and have your new water at 1.024 with 20% daily changes, your tank will trend to 1.0267. If in that same setup, your evaporation is only 4 oz/day, you'd trend toward 1.0246, which is a tad low, but probably okay for most things. If I'm vaguely right that evap will stay between a half cup and two cups per day, then you might be just fine, at least if you keep less sensitive species

It is about 2 cups a day, my lights are very close to the surface and I have high surface agitation. This was my initial thought. Without doing math I can mix up my 1.026 for the week and then just add the total I expect to evap. 

It has the benefit of never adding RODI to the tank directly so the salinity would fluctuate less daily, as obrien said.

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reasonable.  Note my math was off by a factor of two (I was using 8 cups per gallon...I hate the imperial system!)

my corrected math says if you're doing 20% daily changes, and evaporating 2 cups per day, you'll need 1.0234 as your new water to stay stable. of course, if for a week you're losing 4 cups/day, you'll want your new water around 1.0205.

Using a constant 1.0234 as your new water, with 20% daily changes:

1 cup daily evap: 1.0247 is equalibrium

4 cup daily evap: 1.0294 is equalibrium

if you use 1.022 as your new water instead, 

1 cup daily evap: 1.0231 is eq

4 cup daily evap: 10.275 is eq

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