I've had 5 Jebao return pumps in use for 3-4 years, you're supposed to clean them? What?
Dual return pumps is always a good idea. I run mine at 100%. Run as much or as little flow as one wants through the sump, I personally don't think it matters. I've ran my tanks at both ends of the flow ranges and it hasn't mattered. I've settled on more flow through the sump because it'll clear the water of floating debris much faster.
Red Dragon used to be the gold standard but now Abyzz takes that title I think. But let's be honest with ourselves, since cheap chinese pumps have been demonstrated to work continuously for years, what's the point in spending $2500+ for an Abyzz? If one has that kind of funds then more power to ya, but for the 95% of everyone else they are simply not an option.
Fwiw, my good friend Bill Bramucci who used to operate Epic Aquaculture had an Abyzz fail on him and cause significant disruptions with his sps tank.
Jay mentions supersaturation as being deadly to fish. Are we talking about when a return pump sucks air in a sump that's low of water and makes a cloud of microbubbles in the display or are we talking supersaturation of O2 levels in the water?
@Jay Hemdal
Supersaturation is caused by air being injected under pressure into the water. It is the nitrogen that causes the issue, not oxygen (that can be held at over120% saturation with no issues, while air, having more nitrogen in it, can cause supersaturation issues at around 105%)
The most common cause is an external pump that develops an air leak on the suction side of the pump. I've also seen it in sumps that get too low, allowing air to vortex into the submerged pump intake.
Here is some text that I wrote up on this issue:
Acute supersaturation
This is known as the “gas bubble disease.” An aquarium that has a water pump malfunction of some sort may develop a dissolved gas saturation level of greater than 110%. The onset is sudden, and the results are devastating. Fish will develop severe bilateral exophthalmia (pop-eye involving both eyes), and their gills will show massive trauma with gas bubble aneurysms. In the worst cases, air bubbles will be present in the soft fin rays and in the gills. Death is rapid, and even if the still-living fish are moved to a new aquarium, they will usually not recover
Two common causes of acute supersaturation are a sump that is allowed to run dry, allowing the pump to suck in air, or a loose fitting that allows for a continuous air leak at the suction side of a pump. Despite best intentions, equipment sometimes does fail, allowing supersaturation to occur.
In these cases, the problem can be lessened by always having the return line from any aquarium pump return water to the aquarium above the water line. The agitation of the pumped water hitting the aquarium surface is akin to shaking up a can of soda pop and driving off the “fizz.”
Not every case of gas buildup in animal tissue is caused by supersaturation. Some bacteria produce gasses as they grow and multiply. A fish with a serious bacterial infection may develop gas pockets in the intestines, behind the eyes, in the air bladder, or even under the skin.
Chronic supersaturation
Only a few aquarists have ever identified this relatively rare, bizarre syndrome. Essentially, this disorder occurs when the level of supersaturation is not great enough to kill the fish outright, but sufficient to cause physical damage to the fish. It is a great mimic of other problems. For example, the damage caused by supersaturation may be invisible to the aquarist, but it weakens the fish. In turn, the fish may develop protozoan infections or may die from a pre-existing chronic problem, such as fatty liver disease.
Since mechanical failure of a pump rarely occurs in a “partial fashion” (that is to say, only a tiny leak develops), this problem is rarely the cause of chronic supersaturation. The primary cause of this malady is the use of very cold tap water (even if subsequently warmed up) to perform partial water changes. During the winter at northern latitudes, the temperature of the tap water may fall to 38 degrees F. At this low temperature, water can hold a huge amount of dissolved gas. In addition, the city water supply may use powerful pumps that force even more gas into solution. When this water is used by unsuspecting aquarists, the result is chronic supersaturation (or even acute supersaturation in severe cases).
One answer to this problem is to warm up the tap water to 85 degrees and aerate it heavily for 48 hours prior to using it for a water change in an aquarium.
The following are symptoms of chronic supersaturation is fishes:
Mostly smaller fish are affected (they have a higher surface-to-volume ratio).
White "mask" on nape of head.
Mild exophthalmia, usually involving both eyes.
Discoloration of posterior soft fin rays.
Missing scales, fin damage (resulting from aggression from the less affected fish).
Fish loss attributed to other chronic problems, such as fatty liver disease.
Gill aneurysms, some macroscopic air bubbles may be seen.
Rapid, deep breathing.
Listlessness, hanging near the surface or on the bottom.
Generally, these symptoms abate only gradually once the source of the supersaturation has been eliminated. In some instances, fish mortality continues for weeks after the incident has been resolved.
