[mr.wilson]

Originally Posted by sphelps

only external/recirculating skimmers have an adjustable turn over rate

Absolutely, you cannot use the type of skimmer feeding that I am recommending with a one pump skimmer where the water feed and air production are produced with one pump. These protein skimmers are less efficient for that very reason. One pump skimmers still benefit from directing the effluent (processed) water to the return pump section of the sump as it allows new unprocessed waster to be pumped through. These types of skimmers function best if they are plumbed directly to the tank with no sump as they process water indiscriminately (no first in first out).

...and none are traditionally gravity fed, unless by gravity fed you simply mean with a pump because no skimmer should be run off gravity (such as straight from overflow) as it will never produce constant flow and cause the skimmer level to be either too high or too low.

The most efficient and quite drain from a surface skimmer is a siphon with an emergency overflow that has a constant slow trickle. There is no "toilet flush" siphon and siphon break with a constant siphon drain so the water level will be constant. A Durso or Stockman drain will also drain steadily if it is vented properly. The only instance that could cause a variation in the drain rate would be a toilet flush of an improperly vented drain. If "X" amount of water goes into a display tank, then "X" overflows at the same rate. The water level in the protein skimmer is regulated by the back pressure of a gate valve and or the height of the drain line.

Also building a separate skimmer chamber which requires a pump to feed water out at the same rate of the skimmer is a new one for me, I have never seen this.

It is a simple idea that greatly improves efficiency that is over-looked.

The 10X turn over recommendation is based on tank/sump flow and not skimmer flow, I have never heard of someone running 10X tank turnover through a skimmer before.

Tank flow rates are governed by closed loop pumps or less effective powerhead systems. Moving water to and from a sump does nothing for tank flow other than a side effect. The purpose of having a sump is to create a remote location to place filtration devices. Once you establish how many GPH these devices require, then you can pick a pump that does moves that much water. Anymore flow redundant at best, but more likely to decrease the efficiency of the filtration devices through a shorter dwell time and less concentrated surface skimming. Excessive, redundant turnover also causes noisy drains, salt creep, micro-bubbles, less surface tension at the overflow, and heat & electrical costs of an oversized pump.

Today's skimmers are not co-current, air stone powered tall structures. They mostly use a single pump and do not offer flow control.

You are correct, most skimmers these days are counter-current. The skimmers that were used in Escobal's work were also counter-current. Almost any protein skimmer can be plumbed for a closed loop (recirculating) pump for bubble production and a secondary feed for throughput of water. Protein skimmers with wood air diffusers introduce more air flow and with smaller bubbles than needlewheel, pinwheel, and venturi aspirated skimmers. The air-driven diffuser skimmer in the skimmer test I sited gave the same results as the downdraft and needlewheel skimmers in the test.

Lastly sumps should be designed to handle the tanks/owners requirement for flow

If you base the design on what you want, then stick with 10x turnover. If you want energy efficiency, better water quality, less noise and micro-bubbles, then size the return pump according to what the filtration requires to operate best.

this is fairly simple and eliminates things like mechanical filtration bypass and would provide adequate contact time for carbon.

No, delivering more water to the sump than the filtration devices require is not simple, it's more complicated and a waste of resources. The only bypass I would recommend is an emergency bypass for the protein skimmer feed incase something gets clogged, but I would have one in place with any drain system that doesn't have an emergency overflow. Todays standards are 20-40 x the volume of the tank in total flow. I go for quality over quantity, but even with the best flow dynamics, you won't achieve this with 10x the volume of the tank.

The worst scenario I come across is what I call a "water mover system". This is a sump with one or two poorly tuned or non-functional filters and lots of water coming and going from the display tank. A lot of resources are used to move the water, but little or no positive gain is achieved. Typically these systems have old carbon that is allowed to leach out any and all TOC (total organic carbon) it has absorbed, UV sterilizers that act only as heaters because the bulbs are expended or burnt out, protein skimmers that don't collect skimmate or sludge in the neck, and refugia that are allowed to overgrow and shadow the lower portions causing a slow unnoticed die-off.