Controllable deep sand beds - a discussion thread

[Sallstrom]

It’s been running a couple of weeks now, I’ve had to adjust the water flow to keep the ORP in the -100 to -250 range if I let it drop to low you get hydrogen sulphide, had it running at -150mv ish for 8 days now and 1 drop every 2 seconds output and just measured nitrates leaving the reactor and they are at 2ppm salifert, so still not completely converting to nitrogen, but nearly there, all being well another week or so and I’ll be at zero. I can see what I assume is nitrogen forming at the top of the cylinder so I have to vent this. I need to make a small adjustment to the outlet tube so this is pushed out moving forward. I’m not seeing any bacteria coming out of the filter as it’s running now, but if I lower the Orp I get a white snot like substance and can smell hydrogen sulphide but this is not what I want, which may be bacteria but I don’t know, I’m trying to avoid this and create nitrogen gas..

Thanks for sharing!
Would be interesting to know pH, KH and Ca in the outgoing water as well. To see if it's also working a bit like a calcium reactor.

 

[Mortie31]

Thanks for sharing!
Would be interesting to know pH, KH and Ca in the outgoing water as well. To see if it's also working a bit like a calcium reactor.

I’ll test them next time I’m testing, would the very coarse sand and LR rubble break down enough to do this?

 

[Sallstrom]

I’ll test them next time I’m testing, would the very coarse sand and LR rubble break down enough to do this?

Great!
It depends on the pH. I'm not sure of your carbon source fed filter, but for example a sulphur filter has a pH around 7,0 and could solve some coral gravel and raise the KH and Ca.
We let the outgoing water from a sulphur filter in a cold water system go through coral gravel on its way back to the sump, but needed to remove it because KH increased too much.

 

[Mortie31]

Great!
It depends on the pH. I'm not sure of your carbon source fed filter, but for example a sulphur filter has a pH around 7,0 and could solve some coral gravel and raise the KH and Ca.
We let the outgoing water from a sulphur filter in a cold water system go through coral gravel on its way back to the sump, but needed to remove it because KH increased too much.

Just measured the PH and it lowers it slightly to 7.85 from 8.3 in my display, I’ll check again when I have it working correctly

 

[Sallstrom]

Just measured the PH and it lowers it slightly to 7.85 from 8.3 in my display, I’ll check again when I have it working correctly

Ah, okey. Big difference compared to a sulphur filter then. Good to know!
Then it shouldn't effect the Ca and KH.

 

[Mortie31]

Ah, okey. Big difference compared to a sulphur filter then. Good to know!
Then it shouldn't effect the Ca and KH.

No not at the moment, but the reactor is still not working optimally I’ll measure again in a month for you and let you know.

 

[Squamosa]

There are a couple of Dymico style filter users on here. The best tank that I have seen using a DIY version is @Squamosa so far.

The guidelines that Dymico state in their manual is, a filter volume of 10%+ of the tank volume. So looking at the filter I have partially complete, it mounts in a 75 G aquarium with a 6" compartment at each end. So this gives the central media compartment a volume of 75G/5' * 4' = 60 G. So this filter should be about perfect for my 560 G DT.

Dennis

That should be more than adequate filter volume!

My filter is now just over a year old, never been shut down (just moved), has never been cleaned because there is hardly any detritus and I really struggle to keep my nitrates above zero. I also shut down carbon (vodka) dosing additions more than six months ago.

 

[Mortie31]

Just an update on my reactor, it’s now working as I hoped, with a through put of 1500ml/hr I get 0 nitrate and the redox is -150 to -250 mv, I’m trying to stabilise this, but I’ve recently switched to a diy NOPOX and it’s far stronger than the aqua forest NPPro I have been using so needing to adjust dose currently at 8ml/day. One thing I’m surprised at again is the amount of gas given off, which I assume is nitrogen, as the redox shouldn’t be low enough for hydrogen sulphide and it doesn’t smell at all.. there is no change in pH or calcium from my tank water.

 

[Mortie31]

That should be more than adequate filter volume!

My filter is now just over a year old, never been shut down (just moved), has never been cleaned because there is hardly any detritus and I really struggle to keep my nitrates above zero. I also shut down carbon (vodka) dosing additions more than six months ago.

Do you have a link to your design at all please?

 

[Dennis Cartier]

That should be more than adequate filter volume!

My filter is now just over a year old, never been shut down (just moved), has never been cleaned because there is hardly any detritus and I really struggle to keep my nitrates above zero. I also shut down carbon (vodka) dosing additions more than six months ago.

I have also been struggling to keep nitrates up, but on a tank that is using a large fuge for export (NO3 currently 0.2 ppm). This got me to thinking about how to avoid this with my future filter build, because having too little NO3 is almost as bad as having too much. My plan is to use an ORP probe to monitor the redox level in the filter, but instead of using it to time the cycles like DyMiCo does, use it to limit the bacterial mat growth by limiting the lowest ORP that the filter runs at.

My reasoning is that if your filter is going into the range that will trigger the production of hydrogen sulfide, the accepted way of dealing with this is to increase the flow to the filter. This in turn will allow the filter to remove more nitrate, which will again cause you to increase the flow, or if you are at an extremely low nitrate level already, to dose nitrate directly.

This is what got me to thinking, would it not be easier to just decouple the amount of water being processed by the filter, and therefore the amount of nitrate being removed. My solution to this will hopefully be to inject air into the circulation side of the filter, to decrease the efficiency, and (hopefully) control the nitrate removal. This should allow the amount of the tank volume and how much nitrate is removed to be affected individually.

Dennis

 

[Mortie31]

I have also been struggling to keep nitrates up, but on a tank that is using a large fuge for export (NO3 currently 0.2 ppm). This got me to thinking about how to avoid this with my future filter build, because having too little NO3 is almost as bad as having too much. My plan is to use an ORP probe to monitor the redox level in the filter, but instead of using it to time the cycles like DyMiCo does, use it to limit the bacterial mat growth by limiting the lowest ORP that the filter runs at.

My reasoning is that if your filter is going into the range that will trigger the production of hydrogen sulfide, the accepted way of dealing with this is to increase the flow to the filter. This in turn will allow the filter to remove more nitrate, which will again cause you to increase the flow, or if you are at an extremely low nitrate level already, to dose nitrate directly.

This is what got me to thinking, would it not be easier to just decouple the amount of water being processed by the filter, and therefore the amount of nitrate being removed. My solution to this will hopefully be to inject air into the circulation side of the filter, to decrease the efficiency, and (hopefully) control the nitrate removal. This should allow the amount of the tank volume and how much nitrate is removed to be affected individually.

Dennis

This is exactly what I’m experiencing in my reactor, for me it’s a balancing act with through flow and carbon dosing, and to keep it nitryfying. I have about an 800L system and the volume of the reactor is 12L, so it will be interesting to see how quickly it controls my tank nitrates currently at 15, or if it’s undersized and doesn’t have much effect, I’m hoping to get the tank levels to about 5.

 

[Mortie31]

I have also been struggling to keep nitrates up, but on a tank that is using a large fuge for export (NO3 currently 0.2 ppm). This got me to thinking about how to avoid this with my future filter build, because having too little NO3 is almost as bad as having too much. My plan is to use an ORP probe to monitor the redox level in the filter, but instead of using it to time the cycles like DyMiCo does, use it to limit the bacterial mat growth by limiting the lowest ORP that the filter runs at.

My reasoning is that if your filter is going into the range that will trigger the production of hydrogen sulfide, the accepted way of dealing with this is to increase the flow to the filter. This in turn will allow the filter to remove more nitrate, which will again cause you to increase the flow, or if you are at an extremely low nitrate level already, to dose nitrate directly.

This is what got me to thinking, would it not be easier to just decouple the amount of water being processed by the filter, and therefore the amount of nitrate being removed. My solution to this will hopefully be to inject air into the circulation side of the filter, to decrease the efficiency, and (hopefully) control the nitrate removal. This should allow the amount of the tank volume and how much nitrate is removed to be affected individually.

Dennis

How would you inject the air? this does sound an interesting way to control efficiency, just wondering if this could be done in a pressurised system, maybe some kind of venturi with a solenoid switch to open or close the air inlet..

 

[Dennis Cartier]

How would you inject the air? this does sound an interesting way to control efficiency, just wondering if this could be done in a pressurised system, maybe some kind of venturi with a solenoid switch to open or close the air inlet..

In my case, I can simply use an air stone or skimmer/venturi pump in the recirculation chamber that pumps water back to the media chamber as they are all open non-pressurized. In your case, because it is pressurized, you would have to form your own venturi on the input side of the powerhead. This could either be a pinch valve (google Bio-Chem pinch valve) or a masterflex fixed speed pump drive with some tough pharmed tubing that can be operated dry, and just pump air bubbles into the recirculation stream. eBay often has 6 RPM fixed speed drives for reasonable money.

This is of course only needed should your filter be able to deplete the nitrate in the tank and leave you with the situation of having to add more/ feed more or lower the removal rate.

Dennis

 

[Mortie31]

In my case, I can simply use an air stone or skimmer/venturi pump in the recirculation chamber that pumps water back to the media chamber as they are all open non-pressurized. In your case, because it is pressurized, you would have to form your own venturi on the input side of the powerhead. This could either be a pinch valve (google Bio-Chem pinch valve) or a masterflex fixed speed pump drive with some tough pharmed tubing that can be operated dry, and just pump air bubbles into the recirculation stream. eBay often has 6 RPM fixed speed drives for reasonable money.

This is of course only needed should your filter be able to deplete the nitrate in the tank and leave you with the situation of having to add more/ feed more or lower the removal rate.

Dennis

Thanks Dennis, I’m going to see how things go over the next few months.. the pinch valve is a good idea and very controllable from my GHL, I've got an few old skimmer pumps in the shed, that I may be able to bastardise to inject air and circulate water through the reactor. I’ll have a mess around when I’m bored..

 

[Mortie31]

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.

 

[Sallstrom]

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.

Nice!
Yes, I believe that's the effect of the carbon source. I've seen the same when dosing into a sand bed.
What I didn't think of back then was to dilute the carbon source to get smaller doses and more stable redox. I think @Lasse is doing that now.

 

[Lasse]

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

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Sincerely Lasse

 

[Val Shebeko]

Following

 

[Val Shebeko]

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

 

[Tajaba]

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.