Algae Scrubber and refugium, same/same or different?

[atoll]

Maxx, Na, as you suspect it's not going to be the case. A fuge is going to be more likely to up your PH. However with regards to the fuges ability to up the PH some of that may depend on the CO2 within the room and high room CO2 can in fact be more troublesome. Even a skimmer may help dissolve an already soluble gas (CO2) into the sump water rather than help dispel it or so I have heard. Size of fuge and amount of algae also being a consideration as to how much CO2 gets used up but then you know that. I guess it all depends on what is most important to you and what is realistically achievable with each. I am probably going to utilise a kalk stirrer soon to add calc but also to help smooth out PH swing and because I don't have a algae head fuge zi have the space to fit one and more.

 

[Maxx]

If the algae is wet it is not [directly] exposed to the air.
Where you can see the algae is wet, but it doesn't appear that water is running down it, try touching it in that place with a finger tip & you'll see that in fact water is running down it. The water will pool around the finger tip.


You seem to have the perception that because algae in a fuge is submerged below the water line it is totally immersed in water, but when algae is suspended on a scrubber screen above the water it isn't immersed, rather it is exposed to air.
This is incorrect.

The entire surface area of algae in a fuge is in contact with water. It is completely immersed.
The entire surface area of algae on a scrubber screen is also in contact with water. A thin film or water, yes,, but totally immersed just the same. So it isn't in direct contact with the surrounding air.

The advantage of growing algae in a scrubber, & why its growth is so consistent & fast, is the environment this thin film of water [the air water interface], creates, because of gas exchange. As a consequence of photosynthesis oxygen levels in aquarium water reach saturation, or near saturation levels, & CO2 levels become limited to the point of photosynthesis ceasing. An algae scrubber can take advantage of this situation via the thin film of water covering its surface as a direct point of gas exchange providing the otherwise limited co2. Either way, the algae on a scrubber screen assimilates all its co2 from the water it is in direct contact with.

cheers

Steve,
I think the debate is in regards to the CO2 absorption at the air/water interface.
Does the constantly flowing water from the ATS allow more CO2 exchange with the surrounding air than a "normal" chaeto refugium, the same amount, or less?

If the algae on the ATS is pulling CO2 from the water, and there is more surface area for the air/water interface, wouldnt that allow for more gas exchange between the two?

Seems as if it would....I'm theorizing here....

 

[Maxx]

Maxx, Na, as you suspect it's not going to be the case. A fuge is going to be more likely to up your PH. However with regards to the fuges ability to up the PH some of that may depend on the CO2 within the room and high room CO2 can in fact be more troublesome. Even a skimmer may help dissolve an already soluble gas (CO2) into the sump water rather than help dispel it or so I have heard. Size of fuge and amount of algae also being a consideration as to how much CO2 gets used up but then you know that. I guess it all depends on what is most important to you and what is realistically achievable with each. I am probably going to utilise a kalk stirrer soon to add calc but also to help smooth out PH swing and because I don't have a algae head fuge zi have the space to fit one and more.

This is what I suspect.

However, you and Steve have brought up some interesting points that I need to consider as well:

I'm going to try using a CO2 scrubber/reactor for my skimmer, and will try the recirculating mod as mentioned here:
https://www.reef2reef.com/threads/the-best-way-to-implement-a-co2-scrubber.330806/

If it works, that should reduce the CO2 levels in the system. If it reduces it too much, I'll be reducing the ability of the algae, (either ATS or chaeto fuge) to photosynthesize and suck up NO3/PO4.

My goal is to get the pH as close to 8.3 as possible, which was always impossible in my previous set up in the basement. 8.05 was about the best I was able to do, even using a chaeto fuge or a Pax Bellum Chaeto reactor. NO3/PO4 reduction was sufficient enough previously that I needed to dose NO3 to the tank.

I do have a kalk stirrer I can use as well if need be.....

So many variables.

 

[atoll]

I think we will have to call it a suck it and see situation. There are so many variables as well and one would need to run both systems one after the other. Even then what size waterfall ATS v what size fuge? Add tin those flow over or through each. Then there is the issue of trends of PH swing/reduction.

 

[Scrubber_steve]

I've never used an ATS, but I've seen several in operation and have never seen a waterfall style ATS where the water completely covers all of the algae and keeps it from being exposed to air during the entire process.

I have a small 6" x 4" scrubber screen, presently with only moderate growth since cleaning, & with what would be considered moderate flow through the algae mass.
I just removed the screen from the unit & directly let the water held within the algae mass pour into a measuring jug. After about a minute, once the water flow slowed to a steady drip, & with the algae mass still completely wet, the measuring jug filled to the 250 ml mark, which is more than a measured cup.
I believe this demonstrates just how much water a scrubber algae mass can hold, despite not being submerged below the water line in a sump. In fact all the algae, other than the outer surface, is submerged in water.

I also measured pH. The display lights at this time had been off for six & a half hours. I have a fish heavy system (some would argue) so plenty of respiration. The reading was 8.3, the same reading I get at peak illumination.

 

[atoll]

Steve, what size gallon wise is your system? My screen is 5"x5" so not so far different to yours. Am running 500liters.

 

[Maxx]

I have a small 6" x 4" scrubber screen, presently with only moderate growth since cleaning, & with what would be considered moderate flow through the algae mass.
I just removed the screen from the unit & directly let the water held within the algae mass pour into a measuring jug. After about a minute, once the water flow slowed to a steady drip, & with the algae mass still completely wet, the measuring jug filled to the 250 ml mark, which is more than a measured cup.
I believe this demonstrates just how much water a scrubber algae mass can hold, despite not being submerged below the water line in a sump. In fact all the algae, other than the outer surface, is submerged in water.

I also measured pH. The display lights at this time had been off for six & a half hours. I have a fish heavy system (some would argue) so plenty of respiration. The reading was 8.3, the same reading I get at peak illumination.

Steve,
What is your display photoperiod?
What is your ATS photoperiod?
If there is any time where the two do not overlap, what is the lowest your pH drops to?

 

[Scrubber_steve]

Steve,
I think the debate is in regards to the CO2 absorption at the air/water interface.
Does the constantly flowing water from the ATS allow more CO2 exchange with the surrounding air than a "normal" chaeto refugium, the same amount, or less?

If the algae on the ATS is pulling CO2 from the water, and there is more surface area for the air/water interface, wouldnt that allow for more gas exchange between the two?

Seems as if it would....I'm theorizing here....

The amount of co2 in the water, & the amount of co2 in the ambient air will determine gas exchange & in which direction it occurs.
This is exactly what I pointed out as the advantage with the scrubber air-water interface in my previous post.

Theoretically, if the co2 level in the aquarium water was greater than ambient air co2 level the gas exchange at the scrubber air - water interface would facilitate a mechanism by which a reduction of co2 in the aquarium water would take place, in the same way as this occurs via protein skimming.

 

[Scrubber_steve]

Steve, what size gallon wise is your system? My screen is 5"x5" so not so far different to yours. Am running 500liters.

I have two screens, both 6" x 4". My system total is around 220 litres. The algae scrubber is the only filtration I use besides filter floss & live rock. I illuminate both screens at the same time - opposite display lights, photo-period about 9 to 12 hours, depending.

 

[Scrubber_steve]

Steve,
What is your display photoperiod?
What is your ATS photoperiod?
If there is any time where the two do not overlap, what is the lowest your pH drops to?

At present I'm running the scrubber photo-period for nine hours a day, opposite the display illumination of 12 hours, so there is a three hour deficit.
My pH measures 8.2 to 8.3 during peak display illumination, or at 3:30am in the morning.

 

[atoll]

I have two screens, both 6" x 4". My system total is around 220 litres. The algae scrubber is the only filtration I use besides filter floss & live rock. I illuminate both screens at the same time - opposite display lights, photo-period about 9 to 12 hours, depending.

My scrubber is undersized but I have offset this to some extent by adding 4 extra red LEDs to my Turbo scrubber turbo charging it. Al9ng with the extra LEDs all have been replaced with Ultra LEDs. I also grow fast growing Ulva intestinalis. Updated this works so well I have to harvest every 4 days.
Pic of my Ulva about to be harvested 4 days since the last harvest, both sides being similar in growth.

 

[Scrubber_steve]

My scrubber is undersized but I have offset this to some extent by adding 4 extra red LEDs to my Turbo scrubber turbo charging it. Al9ng with the extra LEDs all have been replaced with Ultra LEDs. I also grow fast growing Ulva intestinalis. Updated this works so well I have to harvest every 4 days.
Pic of my Ulva about to be harvested 4 days since the last harvest, both sides being similar in growth.

how many hours a day are you running the scrubber photo-period?

 

[atoll]

how many hours a day are you running the scrubber photo-period?

20 to 4

 

[Scrubber_steve]

20 to 4

I've run my photo-period at 24/7. The growth initially is turbo-charged, for a couple of weeks maybe. But then the NO3 & PO4 start to bottom out way beyond test kit zero readings & the growth stalled.
If I only ran one screen at 24/7 , probably no problem?

Running a photo-period of 7 hours still controls the nutrients, albeit they rise some, but growth is much slower. I revert to this if I go away for a few weeks so maintenance is greatly reduced.

 

[Maxx]

The amount of co2 in the water, & the amount of co2 in the ambient air will determine gas exchange & in which direction it occurs.
This is exactly what I pointed out as the advantage with the scrubber air-water interface in my previous post.

Theoretically, if the co2 level in the aquarium water was greater than ambient air co2 level the gas exchange at the scrubber air - water interface would facilitate a mechanism by which a reduction of co2 in the aquarium water would take place, in the same way as this occurs via protein skimming.

Theoretically, yes.
Under what circumstances would the tank water have more CO2 than the surrounding environment?

What is more likely to happen is that you are adding CO2 to the system instead of reducing it.

 

[atoll]

I've run my photo-period at 24/7. The growth initially is turbo-charged, for a couple of weeks maybe. But then the NO3 & PO4 start to bottom out way beyond test kit zero readings & the growth stalled.
If I only ran one screen at 24/7 , probably no problem?

Running a photo-period of 7 hours still controls the nutrients, albeit they rise some, but growth is much slower. I revert to this if I go away for a few weeks so maintenance is greatly reduced.

Except my screen needs to be at least half the size again plus I only got my scrubber online after my nitrate reached 80ppm due to the fact the LEDs needed replacing. I might up the lighting period to 24/7 and see if my nitrate comes down faster as it is only reducing very slowly.

 

[Shinister]

Theoretically, yes.
Under what circumstances would the tank water have more CO2 than the surrounding environment?

What is more likely to happen is that you are adding CO2 to the system instead of reducing it.

A calcium reactor will lower a tanks PH and it may cause more CO2 in the tank than the surrounding environment. I use a CO2 scrubber to keep my PH up. It's a new house with an energy star rating so it's sealed pretty good so a combination of that and the calcium reactor will make my PH go south of 8.

 

[atoll]

A calcium reactor will lower a tanks PH and it may cause more CO2 in the tank than the surrounding environment. I use a CO2 scrubber to keep my PH up. It's a new house with an energy star rating so it's sealed pretty good so a combination of that and the calcium reactor will make my PH go south of 8.

Which is why a kalk stirrer maybe a better option.

 

[Scrubber_steve]

Theoretically, yes.
Under what circumstances would the tank water have more CO2 than the surrounding environment?

This is a very common occurrence during the night cycle on a tank without algae filtration, & why pH falls - biological processes of photosynthesis are the opposite when light isn't provided. Photosynthesising organisms in the display - corals, algae, cyano, dinos, diatoms, respire carbon dioxide, along with fish & other organisms.

What is more likely to happen is that you are adding CO2 to the system instead of reducing it.

When ambient air co2 is higher than fresh air levels a skimmer for sure increases the co2 content of water because the co2 is being aggressively forced into the water via bubbles. The interaction via the air-water interface by a scrubber however is passive, & during photosynthesis what ever level of co2 does cross over into the water is used by the algae, as I've already pointed out.

It seems you have made up your mind on this subject, so I'll leave it at that.

 

[Scrubber_steve]

Except my screen needs to be at least half the size again plus I only got my scrubber online after my nitrate reached 80ppm due to the fact the LEDs needed replacing. I might up the lighting period to 24/7 and see if my nitrate comes down faster as it is only reducing very slowly.

Plenty of people run their fuges 24/7 on a permanent basis. Give it a go untill NO3 levels come down.
Don't forget your scrubber is dealing with the daily feedings of the tank, which is what its designed to do. Your adding on the extra task of reducing high levels of nitrate already in the system.

What are these "Ultra LEDs" you added to your scrubber?