DSB vs. Settling Tank

[uryy4me]

Why the heck would I want a DSB when I can use a settling tank to do everything a DSB could do for me? (and I just found out 5 minutes ago what a settling tank is so please feel free to set me straight on the virtues of one )

[cyberchef]

The settling tank won't do everything a DSB will... It willnot process the waste nor will it process nitrates... It will allow the detritus to settle so that you can easily siphon it pout and then you don't have to worry about processing it... The only down side I know of is you have to have room for it...

[Geoff]

Originally posted by cyberchef
The only down side I know of is you have to have room for it...

this can be a huge downside. a settling tank needs to be a place where the velocity (not flow) of the water is slow enough that gravity takes over on the detritus and allows it to fall to the bottom of the tank. the problem is that in order to slow the velocity down you need to increase the size of the tank ( i do not know the math here for velocities and area for water). the greater the flow the harder it is to slow down the velocity of water. this is exactly the same problem people have with bubbles in the sump. you have to slow the water down in the sump so the bubbles can evacuate the water column before being pumped into the display. the same is for the detritus, but with detritus gravity is the driving force for the detritus in leaving the water column.

you want as much flow through the settling tank as possible. the greater the volume of water through the settling tank the more efficient the system will be at removing the end detritus.

G~

[uryy4me]

hmm, I have about 1000gph flowing into a 60g long shallow stock tank and my input is done via one of those SCUID things (I bought one and could not find any good use for it in my displays so I am playing w/ it here). I don't know the slightest thing about fluid dynamics or where stuff would settle which is kinda why I posed the question in the first place

[uryy4me]

Originally posted by cyberchef
The settling tank won't do everything a DSB will... It willnot process the waste nor will it process nitrates... It will allow the detritus to settle so that you can easily siphon it pout and then you don't have to worry about processing it... The only down side I know of is you have to have room for it...

maybe a stupid question, but with a bunch of LR in the display and a removal of the "junk" in the settling tank why would I have a nitrate problem ?


just to be clear, I have a reasonable envestment in my DSB (I couldn't get SD here in MN, so 600 lb shipped in was not pocket change), but I am open to opinions and will admit mistakes and alwyas am looking to seek out better options1

[MiddletonMark]

Did you have a setup with big nitrate problems; so set this one up with a DSB?

Or did you just hear about DSB, and start with that?

I don't want to antagonize, but I think that nitrate-fear caused a lot of people to go with DSB's; and that while it might be a little harder to have nitrates `undetectable' without a DSB - mine are nearly so without a DSB.

Of course, ask me in a few years and maybe I'll be struggling; but siphoning of my sump [with settled material] and substrate [settled material] with no DSB seems fairly effective in my experience.

[SPC]

Originally posted by Geoff
this can be a huge downside. a settling tank needs to be a place where the velocity (not flow) of the water is slow enough that gravity takes over on the detritus and allows it to fall to the bottom of the tank.

I agree Geoff. Another possible solution is to run only part of the water (50% maybe) through the settling tank... or use a filter pad to help catch the detritus... and if a filter pad is employed, is there any need for a settling tank.

I wonder if we should try and address a few points first before going on.

1. In order to make a settling tank, remote DSB, filter pad etc... work, the detritus must make its way out of the main tank. How many of us have enough water movement in the main tank to accomplish this? For those who do not (like me), are we willing to manually cause a storm at least once/week in order to get the detritus to move to the removal site?

2. Liquid waste from our animals cannot be removed in the same manner as solid waste can, how do we know that we are removing enough of this waste to keep from having a build up of the end product (nitrate, phosphate)? Will an efficient skimmer, LR, water changes be adequate to keep up with this end product caused by liquid waste?

3. If we employ a settling tank, what is the minimum time frame for removing detritus? In other words, if the detritus is allowed to sit in the settling tank for 2 weeks, is this time period adequate?
I do a water change every 3 weeks, if I allow the detritus to sit there for this length of time, have I really accomplished anything?
Steve

[Spanky]

Exactly Mark,

Remember when this started people were running wet/dry, bare bottom, and live rock.

[mojoreef]

Well I am bored so maybe I can take a shot at this one. Steve let me address your concerns

1. In order to make a settling tank, remote DSB, filter pad etc... work, the detritus must make its way out of the main tank. How many of us have enough water movement in the main tank to accomplish this? For those who do not (like me), are we willing to manually cause a storm at least once/week in order to get the detritus to move to the removal site?

This is one of the problems I feel most hobbists have. Pour water circ.. If you dont design your circ.. to get the detritus out and into say...the settling tank...then your display will become the settling tank

2. Liquid waste from our animals cannot be removed in the same manner as solid waste can, how do we know that we are removing enough of this waste to keep from having a build up of the end product (nitrate, phosphate)? Will an efficient skimmer, LR, water changes be adequate to keep up with this end product caused by liquid waste?

Well I dont think this question really pertains to a settling tank or not but what they heck . Good flow brings this kinda waste to places it can be processed. Places like LR pours, skimmers, and so on and so on.

3. If we employ a settling tank, what is the minimum time frame for removing detritus? In other words, if the detritus is allowed to sit in the settling tank for 2 weeks, is this time period adequate?

Steve the time frame could be what ever you wanted, based on your feeding habits and bio load. A true settling tank is very deep and tends to isolate the fall out. I am pretty sure 2 weeks would be fine.

ok this pot has been stirred enough

Mike

[uryy4me]

Any advise on how to best determine if you have enought flow to push detritus out of the display?

I suspect a simple x times turnover is not all that applicable and I am not interested enough to pull all of the substrate out of my tank only to monitor accumulation ...so maybe this just remains a mystery?

- scott -

[mojoreef]

Hey Scott your right its not an easy one. First you will need a good pull from your overflow. This would mean that anything up high in the water column would end up being pulled into the overflow. Next would be a good source of waterflow that randomises the water in the tank. if the column is stirred in many different direction it will eventually end up close to the overflow pull and then in it goes. YOur not going to get it all, but you can make a good dent.


Mike

[Spanky]

I get all of mine.

[mojoreef]

I get pretty close to all of mine to, but we dont have a sandy substraight to protect. I did a vac last night and thier was hardly anything in the CC in the way of detritus, and it had been 2 months.

Mike

[Geoff]

Originally posted by SPC
...... through the settling tank... or use a filter pad to help catch the detritus... and if a filter pad is employed, is there any need for a settling tank.

a filter pad/sponge is the method i use for cleaning out detritus. i do not have room for a settling tank so i use sponges. it means i need to clean them out a lot more than if i had a settling tank.

G~

[uryy4me]

the teeth on my overflow are a good 2-2.5" deep and I am pushing about 3800 gph out of the tank into a sump...is that enough on a 285 (I also have 2 closed loops pushing about 2800 each and intend to add a couple Tunze's for randomization and flow). If I were to push water to a settling tank from the sump where it would drain via a surface skimmer what sort of flow rate would be reasonable (e.g. would 700gph into a 60g settling tank be too much flow)?...sounds like this may make for an interesting winter project