In his recent "Advanced Aquarist" article on plumbing a manifold (http://www.advancedaquarist.com/issues/ ... /short.htm), Anthony Calfo made a few remarks about the adequacy of overflow rates in prebuilt "reef-ready" tanks. Basically, he wasn't impressed. When looking at the "All Glass" offerings, I'll admit that I'm not impressed with their overflow capacity either (though there are other manufacturers with more substantial "reef ready" overflows on their tanks). But even if I'm not personally impressed with the "All-Glass" design, should that really matter to people buying a tank? Is the "All-Glass" "reef ready" tank really inadequate to the task?
The proposal he makes in his article is that advanced aquarists should use the sump water circuit with a return line manifold to supply all of the water movement in the main tank, thereby eliminating the need for the powerheads that "novice aquarists" are more prone to use. While I agree that the manifold he presents provides better control over the return line's static flow than the more typical single or double outlet, I don't think he presents a sufficiently convincing argument that the sump circuit should supply all of a tanks water movement for any reef tank, let alone the reef tanks of those Anthony thinks of as "advanced aquarists."
First of all, his proposal doesn't make much of an accomodation for variable flow. The value of variable flow to sessile and motile tank inhabitants has been clearly presented more and more often in various forums, in trade magazines (including "Advanced Aquarist") and at industry conferences. The manifold idea could be modified to allow moderate variations of flow with a solenoid valve on one or two of the outlets, but solenoid valves are complex, bulky and expensive, and tuning the system to get a specific pattern of variable flow seems annoyingly difficult. Adjusting the configuration to respond to changes seems even less practical. Other means of obtaining variable flow (variable speed propellor pumps, sea swirls, dump buckets, etc.) are simpler, easier to configure precisely, and trivial to reconfigure when conditions change.
Second, his proposal for large quantities of tank turnover through the sump circuit directly conflicts with other goals of many aquarium owners. Overflows and sump drains become increasingly noisy and at risk of floods when driven at or past nominal capacity. Because I believe in redundancy, I have two overflows and two drains in my tank, each of which is normally running at 1/2 capacity (so that if one gets clogged, the other can handle the full load without risk of dumping tank contents on the floor). To size this approach for a moderate 10x turnover in a 120 gallon tank would require that each drain be able to handle 1200gph or be a minimum of 1.5" PVC. To stuff a 1.5" bulkhead into a 6"x6" overflow box with anything else is a bit of a challenge. A Durso Standpipe properly sized with 2" PVC will fill the entire overflow box if it fits at all. 8"x8" and larger overflow boxes, while capable of handling the larger drain components, quickly consume unacceptably large fractions of tank volume. Further, in my opinion, huge overflow boxes are at least as obtrusive and ugly as the powerheads mentioned as being so unattractive in the article.
One solution is to give up on redundancy. So few other aquarists have redundant equipment or even a tank design that gracefully handles the failure of individual components. Even Anthony's advanced strategies are quite happy putting 100% of the tank's circulation under the control of "a single cool-running external pump." Why should I care about it? My feeling here is that redundancy increases the chance that my pets will not be harmed and will continue to be healthy even if I leave the house and something breaks down while I'm away. I also hope that effective planning (including redundancy) will result in fewer house damaging accidents of the type that I read about so frequently in these forums (...woke up the next morning, 30 gallons of saltwater on the rug. argh!). Redundancy seems to be a less expensive alternative to plans with single points of failure when examined over the longer term. So far, so good.
If I have redundant drains in a 120gallon tank, 1" drains in 6"x6" overflow boxes appears to be a fairly practical choice that leaves most of the tank volume intact, and also leaves space in the overflow box for a 3/4" return line bulkhead. Which means that the sump return flow rate is limited by the capacity of one 1" drain, or 600gph, or 5x hourly turnover. Given these practical sizing selections, supplemental main tank circulation seems to be in order to keep all of my reef critters happy and healthy. Supplemental circulation also allows me to have lower power circulation pumps in the main tank that can continue to operate for long periods of time during larger scale emergencies like power failure or a substantial leak.
Anthony's criticisms of powerheads include appearance, efficiency, heat, and risk of electrocution. As he already described, the electrocution risk can be managed with GFCI's on all pump circuits (I like one GFCI per pump, so that one pump's failure doesn't take out anything else). As to efficiency and heat generation, propellor and other axial flow pumps seem to have an excellent answer. Pumps like Jimmy Chen's modified Little Giants and the Tunze Turbelle Stream pumps can't lift water more than an inch or two. But they can move enormous volumes at moderate velocities and very low power consumption (15W for 1800gph of speed controlled flow with the Tunze 6000, compared to 145W for the 1800gph Mag18 pump). As for the appearance of these pumps, well, we all have different tastes. Like Anthony, I'm not a big fan of chunks of black plastic glommed on the walls of my tank, but once a pump gets covered with corraline algae, I stop noticing them and just start appreciating them for the benefits they give my animals.
The biggest issue with propellor pumps appears to be price and build quality. Tunze is the first company with a mass market product and their product is shockingly expensive while being built out of rather flimsy components. IMHO, they're still worth it, but I hope that other manufacturers react to the opportunity there and quickly provide competing products to fill the market need for low-head, moderate-velocity, high-volume circulation pumps. Eductors may provide a partial solution as they do increase the volume and decrease the velocity of a pump's output, but they require a power hungry and relatively inefficient high head pump to function properly.
To conclude my critique of Anthony's article, I want to acknowledge that the concept of a return manifold has a lot of merit and that I'm building one for my own tank this weekend, taking into account some of his suggestions. However, to conclude that the manifold can or should be the only circulation for a show tank doesn't appear justified. It doesn't take into account nearly enough of the other issues that we as aquarists will individually balance when planning and setting up our tanks. I know that I'm an oddball when it comes to redundancy in my aquarium but I'm not the only one concerned about noise or floods and I'm absolutely not alone in disliking large overflow boxes in my tank. Once it's been concluded that there's no real reason to try to put 10x or more of the tank volume through the tank's overflows and drains, even the smallish All-Glass overflow designs appear adequate to the needs of the novice or advanced hobby aquarist. At least, that's my take on the subject.
Regards,
Ross
The proposal he makes in his article is that advanced aquarists should use the sump water circuit with a return line manifold to supply all of the water movement in the main tank, thereby eliminating the need for the powerheads that "novice aquarists" are more prone to use. While I agree that the manifold he presents provides better control over the return line's static flow than the more typical single or double outlet, I don't think he presents a sufficiently convincing argument that the sump circuit should supply all of a tanks water movement for any reef tank, let alone the reef tanks of those Anthony thinks of as "advanced aquarists."
First of all, his proposal doesn't make much of an accomodation for variable flow. The value of variable flow to sessile and motile tank inhabitants has been clearly presented more and more often in various forums, in trade magazines (including "Advanced Aquarist") and at industry conferences. The manifold idea could be modified to allow moderate variations of flow with a solenoid valve on one or two of the outlets, but solenoid valves are complex, bulky and expensive, and tuning the system to get a specific pattern of variable flow seems annoyingly difficult. Adjusting the configuration to respond to changes seems even less practical. Other means of obtaining variable flow (variable speed propellor pumps, sea swirls, dump buckets, etc.) are simpler, easier to configure precisely, and trivial to reconfigure when conditions change.
Second, his proposal for large quantities of tank turnover through the sump circuit directly conflicts with other goals of many aquarium owners. Overflows and sump drains become increasingly noisy and at risk of floods when driven at or past nominal capacity. Because I believe in redundancy, I have two overflows and two drains in my tank, each of which is normally running at 1/2 capacity (so that if one gets clogged, the other can handle the full load without risk of dumping tank contents on the floor). To size this approach for a moderate 10x turnover in a 120 gallon tank would require that each drain be able to handle 1200gph or be a minimum of 1.5" PVC. To stuff a 1.5" bulkhead into a 6"x6" overflow box with anything else is a bit of a challenge. A Durso Standpipe properly sized with 2" PVC will fill the entire overflow box if it fits at all. 8"x8" and larger overflow boxes, while capable of handling the larger drain components, quickly consume unacceptably large fractions of tank volume. Further, in my opinion, huge overflow boxes are at least as obtrusive and ugly as the powerheads mentioned as being so unattractive in the article.
One solution is to give up on redundancy. So few other aquarists have redundant equipment or even a tank design that gracefully handles the failure of individual components. Even Anthony's advanced strategies are quite happy putting 100% of the tank's circulation under the control of "a single cool-running external pump." Why should I care about it? My feeling here is that redundancy increases the chance that my pets will not be harmed and will continue to be healthy even if I leave the house and something breaks down while I'm away. I also hope that effective planning (including redundancy) will result in fewer house damaging accidents of the type that I read about so frequently in these forums (...woke up the next morning, 30 gallons of saltwater on the rug. argh!). Redundancy seems to be a less expensive alternative to plans with single points of failure when examined over the longer term. So far, so good.
If I have redundant drains in a 120gallon tank, 1" drains in 6"x6" overflow boxes appears to be a fairly practical choice that leaves most of the tank volume intact, and also leaves space in the overflow box for a 3/4" return line bulkhead. Which means that the sump return flow rate is limited by the capacity of one 1" drain, or 600gph, or 5x hourly turnover. Given these practical sizing selections, supplemental main tank circulation seems to be in order to keep all of my reef critters happy and healthy. Supplemental circulation also allows me to have lower power circulation pumps in the main tank that can continue to operate for long periods of time during larger scale emergencies like power failure or a substantial leak.
Anthony's criticisms of powerheads include appearance, efficiency, heat, and risk of electrocution. As he already described, the electrocution risk can be managed with GFCI's on all pump circuits (I like one GFCI per pump, so that one pump's failure doesn't take out anything else). As to efficiency and heat generation, propellor and other axial flow pumps seem to have an excellent answer. Pumps like Jimmy Chen's modified Little Giants and the Tunze Turbelle Stream pumps can't lift water more than an inch or two. But they can move enormous volumes at moderate velocities and very low power consumption (15W for 1800gph of speed controlled flow with the Tunze 6000, compared to 145W for the 1800gph Mag18 pump). As for the appearance of these pumps, well, we all have different tastes. Like Anthony, I'm not a big fan of chunks of black plastic glommed on the walls of my tank, but once a pump gets covered with corraline algae, I stop noticing them and just start appreciating them for the benefits they give my animals.
The biggest issue with propellor pumps appears to be price and build quality. Tunze is the first company with a mass market product and their product is shockingly expensive while being built out of rather flimsy components. IMHO, they're still worth it, but I hope that other manufacturers react to the opportunity there and quickly provide competing products to fill the market need for low-head, moderate-velocity, high-volume circulation pumps. Eductors may provide a partial solution as they do increase the volume and decrease the velocity of a pump's output, but they require a power hungry and relatively inefficient high head pump to function properly.
To conclude my critique of Anthony's article, I want to acknowledge that the concept of a return manifold has a lot of merit and that I'm building one for my own tank this weekend, taking into account some of his suggestions. However, to conclude that the manifold can or should be the only circulation for a show tank doesn't appear justified. It doesn't take into account nearly enough of the other issues that we as aquarists will individually balance when planning and setting up our tanks. I know that I'm an oddball when it comes to redundancy in my aquarium but I'm not the only one concerned about noise or floods and I'm absolutely not alone in disliking large overflow boxes in my tank. Once it's been concluded that there's no real reason to try to put 10x or more of the tank volume through the tank's overflows and drains, even the smallish All-Glass overflow designs appear adequate to the needs of the novice or advanced hobby aquarist. At least, that's my take on the subject.
Regards,
Ross
