Controllable deep sand beds - a discussion thread

[Val Shebeko]

Ahem if i may.......... Since your PH is probably somewhere around 7.8 or lower in the DSB due to lack of oxygen and probably alot of CO2, the aragonites are dissolving and hence your higher Alkalinity.

Dymico actually uses this to their advantage like a built-in CaRx which is pretty neat if you got the time to code and pH sensor probe.

Thinking you got it just right. The rest of your comment I don’t understand.

Is there a short term fux while I go for a ride on the learning curve ?

 

[Val Shebeko]

Who sells these things un the USA ? Glad I asked.

 

[Dennis Cartier]

Hi All, not sure if I’m interpreting this correctly or not, but I have been trying to stabilise the redox levels and through flow in my reactor. I was dosing Vand V mix 12 x a day, and looking at the plot on my GHL I saw a very regular pattern, i knew bacteria used carbon as a food source, but I didn’t expect it to be such a quick response and also how quickly it was depleted, however I’m not sure is the change in redox due to bacteria process or am I barking entirely up the wrong tree. When I switched to 24 doses the levels flattened out dramatically.. I’m not sure if this has any impact or not, any thoughts @Dennis Cartier @Lasse @Jomama
I’ll track it over the next few days.

Yes, as you have probably figured out by now, the carbon addition has a very large impact on redox, and quite quickly. The DyMiCo filter takes advantage of this fact, dosing carbon once per hour, and altering the amount dosed based on the duty cycle of the filter. The faster the redox drops, the faster the cycle must end (flush), to limit the range of the redox. They target a maximum of 15 cycles per hour, so the shortest cycles are 4 minutes and the longest are 1 hour (they flush at least once per hour).

Dennis

 

[Dennis Cartier]

Who sells these things un the USA ? Glad I asked.

The DyMiCo filters are only for sale in Europe at this time. I believe in Holland. I am not sure if they have any plans to bring them to North America.

To expand upon the explanation. They (DyMiCo) place a PH probe in the recirculation chamber of their filter and add CO2 using an air stone to control the PH of the filter media. The bottom section of their filter uses large size media (like CalRx media), and it is this area of their filter bed that gets dissolved. They recommend a starting PH range of no lower than 7.6 when putting one of their filters into service, and then adjusting the PH level lower after they effects on the Ca/Alk are established.

For my DyMiCo style filter, I have not yet decided about using CO2 addition for the CalRx effect. Because the number of cycles are variable, and will probably change depending on nitrate/bacterial levels, my concern is that this may result in fluctuating Alk/Ca levels. My hope is that I will be able to establish a relationship between the number of cycles, the fixed volume of water I will be returning and the PH level of the filter bed, to allow me to calculate the impact on the Ca/Alk levels.

Dennis

 

[Lasse]

Hey guys. Got a question. I am getting extremely high dKH in my dsb. Started a couple of weeks ago. A ybthoughts on this ?

Ahem if i may.......... Since your PH is probably somewhere around 7.8 or lower in the DSB due to lack of oxygen and probably alot of CO2, the aragonites are dissolving and hence your higher Alkalinity.

Dymico actually uses this to their advantage like a built-in CaRx which is pretty neat if you got the time to code and pH sensor probe.

The post of @Tajaba can be one explanation but there can be others, If there is a high NO3 level in the tank and the alkalinity suddenly start to rise - in the tank (or in the DSB as a start) it can bee a sign of a denitrification process that just have started.

In a special designed FW fish farm system, where I have been involved in the design process, we always see an alkalinity rise when the denitrification process in our filter kicks in after a month or two. Because of heavy feeding the NO3 level at that time can be around 200 - 300 ppm. No WC. Suddenly we can see that the alkalinity rise from the wanted 3-5 dKH (needing for good nitrification and regulated by adding NaHCO3) up to sometimes over 30 dKH (depending on the NO3 level at start) When the stored NO3 is used - the alkalinity starts to drop again. This special system does not rely on added DOC (as suger, alkohol or other soluble organic carbon sources) - we let the anaerobic processes in the filter make them by their self.

My question is - what´s your NO3 level? Before and at the moment? Do you have a reversed flow through the DSB?

Sincerely Lasse

 

[Mortie31]

Here is my graph below my sandbed. I dose around o.1 ml 5 % ethanol every 20 minutes since 12:00 the 31/8 - before it was every 30 minutes. At -15 mV my pump start to pump. I use pulse variable and it will pump for 2 sec and wait for 15 sec. I have pump that´s to large. I would like a dosing pump but I can´t have that for the moment,

Just now - there goes around 60 litres 24 hours through my sand bed. Sample time is 1 minute

​

Sincerely Lasse

Thankyou Lasse, I like the idea of using pulse variable, I use it to keep my temp stable and hadn’t thought of it in this situation. Looking at your graph you still get a large redox swing +/- 80mv ish, do you think this is optimal or would less variation benefit further? With your flow rate through your sand bed do you get 0 nitrate?

 

[Mortie31]

Yes, as you have probably figured out by now, the carbon addition has a very large impact on redox, and quite quickly. The DyMiCo filter takes advantage of this fact, dosing carbon once per hour, and altering the amount dosed based on the duty cycle of the filter. The faster the redox drops, the faster the cycle must end (flush), to limit the range of the redox. They target a maximum of 15 cycles per hour, so the shortest cycles are 4 minutes and the longest are 1 hour (they flush at least once per hour).

Dennis

Thanks Dennis, I’m hoping you or other readers can help me understand the process here, as you say the very rapid drop in redox following carbon dosing can be seen and also how quickly it rises again, now my question is, what are we actually seeing here? Is the initial drop due entirely to the carbon affecting the conductivity then the subsequent rise due to bacteria removing the carbon from the water column? Or is it due to denitrifying bacteria reducing O2 when the carbon is first dosed then slowing down as it’s levels are exhausted. I may well be trying to find a link that isn’t there but trying to understand what’s happening here.
Paul

 

[Lasse]

IMO - In our aquaria - the demand for DOC both for growth and for the denitrification process in anaerobic conditions are huge. The bacteria will react on every molecule of DOC - directly. It is very important to stress that these two processes that demand DOC is two total different processes and at least I think that the denitrification process will affect the redox directly. IMO - even the growth process during anaerobic conditions will change the redox - growth process during aerobic conditions - not sure but at probably not in a significant way. The last statement I´m very unsure of - have not done any studies on that. The other thing that effect the redox is the oxygen content of the water. In a anaerobic condition many bacteria are facultative - it means that they can change between aerobic and anaerobic conditions very fast. If they use oxygen (the small amount that´s come in through the pump ) they will change to oxidative processes - by definition - rise the ORP readings. This is fast processes and it is very difficult to manage this in a good way without fast changes. My measurements is taken every minute - the graph below shows the processes for every minute the last half hour. The pump start at -15 mV and for the moment I use 2 sekonds on and 30 sec paus.

The problem is to find the right values of pulse and paus. I´m in my learning curve for this. But it will probably change with time anyhow because the bed will in some situation produce the needed DOC by itself because I do not use any flush through like the Dymico. I want this to happen - that I do not need to add any external DOC

If it have affect the NO3 - I can´t answer that - I have add NO3 for 1.5 year to the system because I have a fuge too. But it is only in the last month I have try to work with the flow and redox in a serious way and last NO3 measurement indicate that NO3 disappear faster than before. I have chose around 0 mV in the plenum because I think it will be lower further up in the bed. I´m thinking of a way to measure the ORP in the middle of the bed too - but I do not want to change for now. I will measure NO3 later today - see what it ends up to today.

I will try to have a smaller dose more often too but I try it out with this 5 % solution first. Will try 2.5 % solution later on. I think it is important with dosing rather often.

Sincerely Lasse

 

[Lasse]

Fine tuning DOC and flow in my plenum. Now the flow around 120 l/24 hours - redox around 0. For the moment 0.06 ml every 4:th minute (2.5 % ethanol). Flow manage by wanted redox value of 0. Pulse variable 2 sec, pause 5 sec. Hysteresis 15 mV

It looks like to dose very small amounts often with a weak solution of DOC is the secret. How I do the small dosing of 0.06 ml? I use a cyclic timer - 239 sec off - 1 sec on. I connect it to a socket (in my case socket 64) I configure a dos pump to lowest speed (that´s for me 3.8 ml/minute (0,06 ml/sec)) I change the Pumps react to from Dosing Schedule to switch channel index 64. I fill up the container and I can see for each day how much I dose/day if I want to calculate that

Sincerely Lasse

 

[Dr. Dendrostein]

Fine tuning DOC and flow in my plenum. Now the flow around 120 l/24 hours - redox around 0. For the moment 0.06 ml every 4:th minute (2.5 % ethanol). Flow manage by wanted redox value of 0. Pulse variable 2 sec, pause 5 sec. Hysteresis 15 mV

It looks like to dose very small amounts often with a weak solution of DOC is the secret. How I do the small dosing of 0.06 ml? I use a cyclic timer - 239 sec off - 1 sec on. I connect it to a socket (in my case socket 64) I configure a dos pump to lowest speed (that´s for me 3.8 ml/minute (0,06 ml/sec)) I change the Pumps react to from Dosing Schedule to switch channel index 64. I fill up the container and I can see for each day how much I dose/day if I want to calculate that

Sincerely Lasse

That's some research, Lasse. You can do it!!!

 

[Mortie31]

Fine tuning DOC and flow in my plenum. Now the flow around 120 l/24 hours - redox around 0. For the moment 0.06 ml every 4:th minute (2.5 % ethanol). Flow manage by wanted redox value of 0. Pulse variable 2 sec, pause 5 sec. Hysteresis 15 mV

It looks like to dose very small amounts often with a weak solution of DOC is the secret. How I do the small dosing of 0.06 ml? I use a cyclic timer - 239 sec off - 1 sec on. I connect it to a socket (in my case socket 64) I configure a dos pump to lowest speed (that´s for me 3.8 ml/minute (0,06 ml/sec)) I change the Pumps react to from Dosing Schedule to switch channel index 64. I fill up the container and I can see for each day how much I dose/day if I want to calculate that

Sincerely Lasse

Excellent Lasse thanks, I’m so glad you have these results, and Ive found exactly the same by increasing the frequency of dosing the redox swings reduce, I’m currently at 96 doses of 0.1ml per day, but i see a larger swing than you do ±50mv.

 

[gregkn73]

Donovan's denitrator which work in a similar way, is more effective with nearly continuous dose =drip dosing of doc. For half an hour ,after dosing 1ml diy nopox ,the water outlet gave 0 no3, instead of 5 at the inlet . So with a drip dosing, it would maximize it's efficiency . But we don't need so effective no3 reducer's no3 are good for our reefs

 

[Mortie31]

Donovan's denitrator which work in a similar way, is more effective with nearly continuous dose =drip dosing of doc. For half an hour ,after dosing 1ml diy nopox ,the water outlet gave 0 no3, instead of 5 at the inlet . So with a drip dosing, it would maximize it's efficiency . But we don't need so effective no3 reducer's no3 are good for our reefs

He certainly came up with a great idea, which I’ve kinda copied and combined it with aquamedics denitrator, which if redox is kept below 350mv ish by and keeping the entire volume of water in the reactor circulating should eliminate the risk of hydrogen sulphide pockets (which was a potential issue with Donovan type reactors). By having very predictable and stable results I’m hoping to be able to control the tank NO3 levels, I currently have NO3 of 15 going in and 0 NO3 exiting so these certainly work. But having a small volume of only 12L total, it will be interesting to see how it keeps up with my tanks 750L ish volume.. and heavy fish load.

 

[MasterBacon]

Any updates?

 

[Val Shebeko]

well , here’s an update.

My dKH was testing at 26, see my previous posts. Here.

Exchanged some email with Dimico this that the other.

Was adding muratic acid to drive down hardmess, adding Mg, adding, adding testing testing.

In a fit pique turned off everything. Unplugged dosing pumps, threw away all the Red Sea, Deep Sea, Uncle Bob’s secret elixer stopped chanting special spells at midnight. Basta!

Started doing 40 gal water changes on a 125 gal tank, 100 gal of water estimated, every 4th day and now every 7th day after 8 water changes , this past
Sat was the 8th dkh isdown to 10 this morning, water chemistry is stable, ph is stable

Call me a new convert to water changes but after three years of water chemistry hell this is the way to go. A few more months and I am going to sell that Apex and the 3 pumps and thousands of dollars of test kits and reagents for 1 dollar to my worst enemy.

I keep excellent records so anyone wants numbers..

Stay tuned.

 

[MasterBacon]

 

[Val Shebeko]

Tellin’ ya. I had run out of ideas and was ready to take the tank down.

Changing 40 gal of water takes a 1/2 hour. Cheap and dirty.

When the hardness falls off a bit more going to try to go to a 2 week schedule.

If anyone is interested I can post numbers . Let me know.

Val

 

[Dr. Dendrostein]

well , here’s an update.

My dKH was testing at 26, see my previous posts. Here.

Exchanged some email with Dimico this that the other.

Was adding muratic acid to drive down hardmess, adding Mg, adding, adding testing testing.

In a fit pique turned off everything. Unplugged dosing pumps, threw away all the Red Sea, Deep Sea, Uncle Bob’s secret elixer stopped chanting special spells at midnight. Basta!

Started doing 40 gal water changes on a 125 gal tank, 100 gal of water estimated, every 4th day and now every 7th day after 8 water changes , this past
Sat was the 8th dkh isdown to 10 this morning, water chemistry is stable, ph is stable

Call me a new convert to water changes but after three years of water chemistry hell this is the way to go. A few more months and I am going to sell that Apex and the 3 pumps and thousands of dollars of test kits and reagents for 1 dollar to my worst enemy.

I keep excellent records so anyone wants numbers..

Stay tuned.

The only thing I use dosing pumps is food for corals and fresh water top off

 

[Mortie31]

Tellin’ ya. I had run out of ideas and was ready to take the tank down.

Changing 40 gal of water takes a 1/2 hour. Cheap and dirty.

When the hardness falls off a bit more going to try to go to a 2 week schedule.

If anyone is interested I can post numbers . Let me know.

Val

What happened with the Dimico?

 

[Dr. Dendrostein]

Fine tuning DOC and flow in my plenum. Now the flow around 120 l/24 hours - redox around 0. For the moment 0.06 ml every 4:th minute (2.5 % ethanol). Flow manage by wanted redox value of 0. Pulse variable 2 sec, pause 5 sec. Hysteresis 15 mV

It looks like to dose very small amounts often with a weak solution of DOC is the secret. How I do the small dosing of 0.06 ml? I use a cyclic timer - 239 sec off - 1 sec on. I connect it to a socket (in my case socket 64) I configure a dos pump to lowest speed (that´s for me 3.8 ml/minute (0,06 ml/sec)) I change the Pumps react to from Dosing Schedule to switch channel index 64. I fill up the container and I can see for each day how much I dose/day if I want to calculate that

Sincerely Lasse

Lasse, did you increase seconds on and seconds off. What timer you using I can use that.