how many times a hour should the water go through the sump?

[MikeInToronto]

To the OP, I believe the recommended rate is ~5x but this is only what I read.

"I saw it on TV so it has to be true!"

[danny zubot]

I was with you up until this post, and that's mostly because I was having trouble understanding both sides until now. However, a tank + sump is a closed system. The amount of water running through the sump should be irrelevant. It would be the same as a HOB skimmer running in a sumpless tank with 100x turnover using just powerheads. In this case, the DT is just like a big sump (since there is no sump).

Water in the sump is the same water as the DT. There is no special separation between the two except the OF, a pump, and some pipe.

The concept that "a sump is not a filter" is a good one. A sump really is nothing except a place to store equipment.

Now if your argument is that a low-flow overflow extracts surfactants better, perhaps you can discuss that more.

That's what I said only in different words. Not to kick a dead horse, but the skimmer controls its own rate of flow through the body of the skimmer. In which case slower is better for extracting surfactants, but only within the skimmer itself. The higher the contact time between the water and the bubbles, the more effective the skimmer is at pulling out waste. This has nothing to do with the rate of flow through the sump, tank, fuge etc.

[golf nut]

Originally Posted by MikeInToronto

Now if your argument is that a low-flow overflow extracts surfactants better, perhaps you can discuss that more.

That is the whole point Mike.

Firstly we all have overflow commonly called prefilter boxes...Why call them this?

Because they are moving the surface water only from the tank when done properly, If you imagined that fish waste, coral waste and detritus was similar to oil it isn't hard to visualize oil floating on the surface of the DT, the prefilter box is there to remove it, the slower the removal the more concentrated that would be , if the extraction rate is increased the oil is mixed with more water and becomes diluted.
So this oil/ water mix then goes to the sump where some use filter sock for containing large bits etc, it then should enter the skimmer as concentrated as possible and then the skimmer can do it's job properly.

Why anyone would want to keep returning dirty water continuously back to the tank so they can keep skimming a little at a time is beyond me, get it out get rid of it and return clean water back to the tank.

[kien]

I've always thought of it this way.. imagine that there is one car wash in the city and all the cars have to go through it. The car wash can only service cars at a certain rate, say 5 cars an hour? Unfortunately the cars can only wait at the car wash for so long before they have to move on (that is they can't sit there forever and wait), so cars are moving through the car wash at a certain rate independent of how fast the car wash can wash cars. As cars come in they get washed, or if they've waited for too long they move on and don't get washed. If cars come in very quickly, obviously fewer will get washed and will just end up passing on through unwashed and so the dirty car ends right back on the streets. If the cars come in slower at a rate that the car wash can handle then more cars will get washed. If it is a perfect day where the rate of cars coming in equals the rate of the cars being washed then all cars will get washed. Also, keep in mind that this is the only car wash in the city so all cars must eventually get washed, so eventually those dirty cars that had to pass through unwashed last time will eventually come back and try again to get washed. The faster they can turn around and get off the streets and come back to the car wash the better their chances of getting washed within a small time frame, but that also means they can't spend as much time at the car wash.

[MikeInToronto]

Originally Posted by Mr OM

That is the whole point Mike.

Firstly we all have overflow commonly called prefilter boxes...Why call them this?

Because they are moving the surface water only from the tank when done properly, If you imagined that fish waste, coral waste and detritus was similar to oil it isn't hard to visualize oil floating on the surface of the DT, the prefilter box is there to remove it, the slower the removal the more concentrated that would be , if the extraction rate is increased the oil is mixed with more water and becomes diluted.
So this oil/ water mix then goes to the sump where some use filter sock for containing large bits etc, it then should enter the skimmer as concentrated as possible and then the skimmer can do it's job properly.

Why anyone would want to keep returning dirty water continuously back to the tank so they can keep skimming a little at a time is beyond me, get it out get rid of it and return clean water back to the tank.

Agreed.

Slowly we can see the use of closed loops falling out of favour because of the high energy costs and a number of other reasons (tank wall integrity, OMs, maintenance, etc). That leaves powerheads and propeller pumps. Many people, a long time ago, decided they preferred to not have PHs in their tanks long term, if not for the appearance, then for safety. That leaves propeller pumps which are very costly once you get beyond, well, one. For this reason I think we will see large volume returns continue.

I don't use a pre-filter so I have nothing to add about that. I do use filter socks but that's just to reduce bubbles in the sump.

[Zoaelite]

Originally Posted by Mr OM

If you skim it 100% then what you return to the tank is clean, if you skim 10% of it then 90% of what you return is dirty or unskimmed, why would you do that when it costs more money in hydro and pumps to do worse?

When it comes down to it a sump has more uses than placing your skimmer in it, extremely slow flow could invoke negative side effects for your reactors, heaters and makes filter socks practically useless.

Do you have any articles that I could read that would sway my opinion? I understand your logic but in a practical setting nutrients are not only on the surface and increasing the flow allows proteins that are dissolved to be removed.

[golf nut]

Originally Posted by zoaElite

When it comes down to it a sump has more uses than placing your skimmer in it, extremely slow flow could invoke negative side effects for your reactors, heaters and makes filter socks practically useless.

In what way could they be problematic how would a filter sock become useless

what should the flow be through the following?

Refugium
UV filter
Charcoal filter
Phosphate filter
Water polisher
etc etc etc.

all are very low requirements, other than the possibility that the skimmer MAY work at 10 times turn over why would you do it?

[Zoaelite]

Originally Posted by Mr OM

In what way could they be problematic how would a filter sock become useless

what should the flow be through the following?

Refugium
UV filter
Charcoal filter
Phosphate filter
Water polisher
etc etc etc.

all are very low requirements, other than the possibility that the skimmer MAY work at 10 times turn over why would you do it?

The filter sock would loose efficiency because it requires high flow to capture as much particulate as possible. You keep restating your point, your logic is understandable but I need some concrete proof (And no I'm not going to call Euro reef and ask them) before I believe it.

The reason I don't believe you is because I own a skimmer, I have 7X turn over in my main tank and still get a very large amount of skimmate production.

If I slowed the flow down even more to the sump would I get more concentrated skimate...? I highly doubt it, again nutrients don't only exist on the surface they are mostly found dissolved in the water column. Considering that letting your skimmer have more access to the polluted water makes more sense.

[freezetyle]

Ha! thats why i love science. Its all conflicting theories.

[Zoaelite]

Originally Posted by freezetyle

Ha! thats why i love science. Its all conflicting theories.

It makes for some good debates. I would say any pump between 500 GPH and 1300 GPH will work for you, draw your conclusions off of what people have posted.