Skimmer functionality when running a scrubber

[Floyd R Turbo]

Thanks to all who have posted and hopefully more will continue to post. As I'm talking to my customers I'm hearing a lot of this - the skimmers work more reliably when a scrubber is also on the system

[Garf]

Might have something to do with this;

http://en.wikipedia.org/wiki/Reactiv...ine_microalgae

Reactive oxygen species are present in low concentrations in seawater and produced primarily through the photolysis of organic and inorganic matter.^[12] However, the biological production of ROS, generated through algal photosynthesis and subsequently 'leaked' to the environment, can contribute significantly to concentrations in the water column.

The production of ROS has also been shown to be dependent on algal cell density. Marshall et al.^[17] found that for Chattonella marina, higher concentrations of cells produced less superoxide per cell than those with a lower density. This may explain why some raphydophyte blooms are toxic at low concentration and non-toxic in heavy blooms.^[50] Tang & Gobler^[51] also found that cell density was inversely related to ROS production for the alga Cochlodinium polykrikoides. They found, in addition, that increases of ROS production were also related to the growth phase of algae. In particular, algae in exponential growth were more toxic than those in the stationary or late exponential phase. Many other algal species (Heterosigma akashiwo, Chattonella marina, and Chattonella antiqua) have also been shown to produce the highest amounts of ROS during the exponential phase of growth.^[50][52] Oda et al.^[16] suggest this is due to actively growing cells having higher photosynthesis and metabolic rates. Resting stage cells of Chattonella antiqua have been shown to generate less superoxide than their motile counterparts.^[53]

The reduction product of superoxide is hydrogen peroxide, one of the most studied reactive oxygen species because it occurs in relatively high concentrations, is relatively stable, and is fairly easy to measure.^[12] It is thought that algal photosynthesis is one of the major modes of hydrogen peroxide production, while the production of H₂O₂ by stressed organisms is a secondary source.^[13][14][15] In marine systems, hydrogen peroxide (H₂O₂) exists at concentrations of 10⁻⁸-10⁻⁹ M in the photic zone,^[15] but has been found in double those concentrations in parts of the Atlantic Ocean.^[35] Its lifetime, ranging from hours to days in coastal waters, can be as long as 15 days in Antarctic seawater.^[12][30] H₂O₂ is important in aquatic environments because it can oxidize dissolved organic matter and affect the redox chemistry of iron, copper, and manganese.^[33] Since hydrogen peroxide, as an uncharged molecule, diffuses easily across biological membranes it can directly damage cellular constituents (DNA and enzymes) by reacting with them and deactivating their functions.^[2] In addition, hydrogen peroxide reduces to the hydroxyl radical, the most reactive radical and the one with the greatest possibility for damage

It is not surprising that ROS production may be a form of chemical defense against predators, since at low levels it can damage DNA and at high levels lead to cell necrosis.^[25] One of the most common mechanisms of cellular injury is the reaction of ROS with lipids, which can disrupt enzyme activity and ATP production, and lead to apoptosis.^[37] Reactions of ROS with proteins can modify amino acids, fragment peptide chains, alter electrical charges, and ultimately inactivate an enzyme's function.^[62][63] In DNA, deletions, mutations, and other lethal genetic effects may result from reactions with ROS.^[64][65] Reactive oxygen species are especially inexpensive to produce as defense chemicals, simply because they are not composed of metabolically costly elements such as carbon, nitrogen, or phosphate. Reactive oxygen species produced by phytoplankton have been linked to deaths of fish, shellfish, and protists, as well as shown to reduce the viability and growth of bacteria.^{[20][50][66][67]} In addition, a study by Marshall et al.^[17] showed that four algal species used as bivalve feed produced significantly lower concentrations of superoxide, suggesting that ROS production by other algal species may be a way to decrease grazing by bivalves. The most direct evidence for ROS as a defense mechanism is the fact that many icthyotoxic algae produce greater concentrations of ROS than nonichthyotoxic strains

It is possible that ROS may not be the actual toxic substance, but may in fact work to make other exudates more toxic by oxidizing them.^[17][68] For instance, ROS from Chattonella marina have been shown to enhance the toxic effects of fatty acid eicosapentaenoic acid (EPA) on exposed fishes.^[17][68] Similarly, free-fatty acids released from diatom biofilms as products of ROS oxidation of EPA are known to be toxic to zooplankters.^[69] In addition, Fontana et al.^[70] suggested that the interaction of ROS and diatom exudates (such as fatty acid hydroperoxides) are responsible for inhibiting embryonic development and causing larval abnormalities in copepods. Finally, ROS oxidation of algal polyunsaturated fatty acids have also been shown to deter grazers.^[71]

In addition to impacting predator-prey interactions, the production of ROS may also help an alga get an advantage in the competition for resources against other algae, be a way to prevent fouling bacteria, and act as a signaling mechanism between cells.^[60][67][72] ROS can inhibit photosynthesis in algae^[25] Thus an alga that is more tolerant of ROS than another may produce and release it as a means of decreasing the other species competitive ability. In addition, Chattonella marina, the most well studied raphydophyte for ROS production, may produce a boundary of ROS that deters other marine microalgae from using nutrients in its vicinity.^[27] Similarly, this boundary could also be a way to discourage bacteria fouling, since the production of ROS is known to inhibit growth and bioluminescent ability in the bacteria Vibrio alginolyticus and Vibrio fischeri, respectively.^[67][72] Lastly, Marshall et al.^[27] showed that Chattonella marina cells were able to change their rate of superoxide production in as little as one hour when in different cell densities, increasing the rate from 1.4 to 7.8 times the original. They suggest that this quick response in altering rates of production may be a form of chemical signaling between cells that works to provide information about cell density.

[Ace25]

To answer the 3 questions in the OP.

1. Produces less skimmate
2. Produces darker and much stinkier skimmate
3. More temperamental, as it can go weeks and not skim more than 1/2" in the cup and then overnight it will overflow the cup with no changes done to the tank or skimmer. The water level is at a constant 9" depth for the chamber the skimmer is in.

[Floyd R Turbo]

Dang! Thought this would be perfectly consistent.

[kotlec]

We talk about scrubber as a standard unit , but never consider what type of algae it is mostly growing. Im not biologist , but thing that different species can have different habits. No ?

[Garf]

We talk about scrubber as a standard unit , but never consider what type of algae it is mostly growing. Im not biologist , but thing that different species can have different habits. No ?

Yes

[kotlec]

[sabbath]

To answer the 3 questions in the OP.

1. Produces less skimmate
2. Produces darker and much stinkier skimmate
3. More temperamental, as it can go weeks and not skim more than 1/2" in the cup and then overnight it will overflow the cup with no changes done to the tank or skimmer. The water level is at a constant 9" depth for the chamber the skimmer is in.

So yours appears to be the exception to many peoples findings. So I wonder if there is something else that you may have changed sense you ran a skimmer without a scrubber. Are you adding something that is causing a reaction with the skimmer in a scrubber system? Maybe it is your nitrates being so low and or your phosphates up is effecting this?

[Mud]

I started my system with a scrubber and a skimmer. For the first 6 months of running this way, the skimmer would go for a day or two without skimming anything then all of the sudden overflow with almost-clear skimmate. During this time, my corals grew beautifully and parameters were all perfect, so I had no complaints. Then I went camping for five days, came home to a burnt-out pump (fed both my display and scrubber). My scrubber screen died, so I took this time to completely redo my sump plumbing and change my scrubber over from CFL to LED. I have found that in the week since my pump blew, my skimmer has produced consistently dark skimmate, which it never did before. I did, however, cut back dramatically on feeding of both frozen foods and liquid coral foods since my scrubber died. Overall, my experience has been that while runner a scrubber my skimmer was way more temperamental. I have yet to see how my skimmer will react to my new scrubber screen maturing, but I'll report my findings.

[sabbath]

I wonder now if there is certain combined filter methods that make the skimmer more or less stable? It would be nice to find the answers to this. As I still am finding it more stable then the same setup was without a scrubber. The only other thing that I can think of that has changed is I'm running less LR.

I'm running skimmer first then Floyd's scrubbers in the sumps. I'm also running a half dose of rox8 in a reactor last that is changed out after a few weeks. I'm doing very little water changes, but when I do I siphon the sand. Oh and minimal LR with a sallow sand bed.

Not sure what is affecting this but this combo is working for 3 systems.