[shelleyo]

My Halimeda is dying and the hair algae and slime algae are flourishing! Also the Button Polyps and Zoas are not opening up. Although the mushrooms, finger leather, brain, and hammers all look great. I have done water changes, added more flow (closed loop and Maxijet 1200) bought new lights, used ChemiClean, and a Poly Filter with no success. Any ideas?

BTW, I also set up a plenum that covers most of the tank bottom in January. Would that have anything to do with it?

PH = 8.4
Calcium - 320
Mag = 325
Alk = 3.0

[Ninong]

Originally Posted by shelleyo

My Halimeda is dying...

Halimeda is a calcareous alga. Therefore it depends on proper levels of calcium, magnesium, alkalinity, etc.

... and the hair algae

Hair algae mainly depends on nitrogen and phosphate and just about any amount of light to flourish.

... and slime algae

"Slime algae" are really cyanobacteria. Will thrive under a lot of different conditions if nitrogen, phosphate, suitable lighting, etc. are present. Does not like strong water currents.

I also set up a plenum that covers most of the tank bottom in January. Would that have anything to do with it?

What exactly do you mean by "most of the tank bottom?" Wouldn't a plenum have to cover all of the tank bottom?

PH = 8.4

This is OK. Anything between 8.0-8.4 is just fine. No problems here.

Calcium - 320

This is too low. Calcium should be around 410 ppm if you want to duplicate natural seawater but most people prefer 425-450 ppm or even 450-475 ppm.

Mag = 325

This is either a typo or a serious problem. NSW magnesium is 1285 ppm.

Alk = 3.0

You didn't give the unit of measurement. If you're talking about 3.0 mEq/l, then you're fine. If you're talking about 3.0 dKH, then it's way too low. NSW = 2.5 mEq/l, which equals 7.0 dKH, but most people prefer to maintain alkalinity a little higher than NSW levels.

[shelleyo]

I am already bringing the calcium up. I know it is too low. I'm not sure about how to figure the Alk and Magnesium from my test kit. The instructions are very confusing. I will go back and test again this evening and maybe someone can help me come up the correct numbers.

The plenum I made extends to about 2" from the sides of the tank so that it doesn't show through the sandbed. I just assumed from reading that one could make the plenum any size they wished. Although I have to admit the clowns have swept the sand from the top of the plenum so that the pvc shows on the corners.

[Ninong]

Here are a few more questions that will help any responders who may wish to offer advice:

What size is your tank?

When was it set up?

When you say, "BTW, I also set up a plenum that covers most of the tank bottom in January," I sort of get the impression that you added a plenum to a tank that was already up and running. Is that correct?

Originally Posted by shelleyo

I am already bringing the calcium up. I know it is too low.

How are you "bringing the calcium up?" What method do you use to maintain calcium and alkalinity?

I'm not sure about how to figure the Alk and Magnesium from my test kit.

What brand of test kits are you using for alkalinity and magnesium? What brand are you using for calcium?

The plenum I made extends to about 2" from the sides of the tank so that it doesn't show through the sandbed. I just assumed from reading that one could make the plenum any size they wished. Although I have to admit the clowns have swept the sand from the top of the plenum so that the pvc shows on the corners.

I should tell you upfront that I am not a fan of plenums. I don't believe they provide any benefits that cannot be obtained with a simple sand bed without the construction of the plenum space.

The plenum method was first advanced by Dr. Jean Jaubert of the Monaco Aquarium. All of his plenums utilized large gravel as the substrate over the plenum. Dr. Jaubert has made various claims about the performance of his plenum systems over the years. Some of his later articles include revisions to some of the claims he made in his earlier articles. It is difficult under any circumstances to compare the sort of plenum equipped reef aquarium one might set up at home with the plenum systems set up by Jaubert because most of us don't have access to the Mediterranean. Some of Jaubert's systems were open and some were closed. The results were significantly different between them.

However, I digress... All plenum systems require the construction of a base that allows for a void space (plenum) beneath a bed of gravel. Most authors who are disposed to write about plenums suggest the plenum space should be ~2 cm. There would be a screen of some sort over this base and then gravel (crushed coral or large particle aragonite sand) is placed on top of this screen. The depth of the first layer of gravel (or coarse aragonite sand) is usually about 5-6 cm. A fine mesh screen material of some sort (inert, of course) is placed on top of this bottom layer of gravel (or large particle aragonite sand). This is to prevent sand-burrowing animals from digging down and disturbing the bottom layer of substrate.

A second layer of sand/gravel is placed on top of the fine mesh screening. This second layer is usually about 6-8 cm deep. The exact depth of each of these two layers depends on the size of the aquarium. Actually, the depth of the aquarium is probably the determining factor that is more important than the overall size of the aquarium.

There is a wide range of opinion on the best particle size range for each of the two substrate layers. Suffice it to say that it isn't a Jaubert plenum system if the particle sizes are too small. Carib-Sea, a vendor of aragonite sand and gravel for marine aquariums, offers suggestions for appropriate particle sizes for plenum systems. Note that they recommend only their three largest particle size products for use in construction of a plenum system. Their Seaflor Special Grade Reef Sand (1-2 mm) is one of the products that I have heard some hobbyists using for plenum systems. Jaubert's original plenums used a particle size of 3-5 cm.

It is important to remember that the purpose of the plenum construction is to isolate a quantity of undisturbed water beneath the sand bed above. Most people who promote plenums recommend building the plenum base so that it comes fairly close to the walls of the tank (1/2" - 1"). That small space between the plenum base and the viewing pane of the tank is just so that the plenum construction is not viewable from outside. However, Julian Sprung has photos of his small plenum system reef aquarium in virtually all of his books and it does not have a space between the plenum base and the glass walls of the tank. His plenum is clearly visible from outside.

An important point is that the space between the plenum base and the tank glass should not be large enough that digging fish could disturb it very far down. This is why you have to set up a mesh barrier between the two layers of substrate over the plenum -- to keep any burrowing fish or other animals from disturbing the bottom layer closest to the plenum area which must be left undisturbed. If your 2" space between the plenum plate and the wall of the tank is large enough that fish or other creatures can dig down close to the bottom, then you could have a problem on your hands.

Recognizing that I am not a fan of plenum systems, I would still like to know how you constructed your plenum? What is the size of the plenum space beneath the substrate? What is the depth of the bottom layer? What is the depth of the top layer? What exactly did you use as sand/gravel? In other words, particle sizes?

As you have probably guessed by now, I am hinting at the possibility that if your plenum was not properly sized and constructed in the first place, you may need to consider removing it entirely.



An Experimental Comparison of Sandbed and Plenum-Based Systems, Part 1 and Part 2.

[shelleyo]

My aquarium is 75 gal with another 6 or 7 in the sump. I have been using Kent Liquid Reactor and Tech-M and Iodine. I add about 1 capful each week. Tech-M on Mondays, Iodine on Wednesdays, and Kent Liquid Reactor on Fridays, plus Purple Up when I think about it.

The tank has been set up for several years but I just added the plenum in January. It is made of 3/4" PVC with screen on top of the first layer of pvc and crushed coral filling the second layer of 3/4" pvc, then fine argonite sand on top of the crushed coral. The plenum extends to about 1 1/2" from the front and sides of the tank but all the way to the back. I don't think I put a screen between the crushed coral and the sand, but I'm not sure.

The test kits I used for the Mag and Alk are Salifert for the Alk and Seachem for the Mag.

[Ninong]

Originally Posted by shelleyo

I have been using Kent Liquid Reactor and Tech-M and Iodine. I add about 1 capful each week. Tech-M on Mondays, Iodine on Wednesdays, and Kent Liquid Reactor on Fridays,...

Suggested reading:

How to Select a Calcium and Alkalinity Supplementation Scheme
http://www.advancedaquarist.com/issues/feb2003/chem.htm

A Simplified Guide to the Relationship Between Calcium, Alkalinity, Magnesium and pH
http://reefkeeping.com/issues/2006-06/rhf/index.php

Iodine in Marine Aquaria: Part I
http://www.advancedaquarist.com/issues/mar2003/chem.htm

Don't add iodine to your tank unless you have tested for it and found it deficient. NSW levels of iodine (all forms) = 0.06 ppm. There is no need to maintain iodine higher than that. Iodine at excessive levels is toxic.

...plus Purple Up when I think about it.

This product is sold by a manufacturer with a lot of aragonite sand on their hands. Their primary business is selling sand. The primary ingredient in Purple Up is fine particle aragonite sand! I guess it's a nice way to get rich if people will actually buy it and believe the advertising claims? IMO it's a complete waste of money but, then again, I'm not the one getting rich selling sand in a bottle.

The tank has been set up for several years but I just added the plenum in January. It is made of 3/4" PVC with screen on top of the first layer of pvc and crushed coral filling the second layer of 3/4" pvc, then fine argonite sand on top of the crushed coral. The plenum extends to about 1 1/2" from the front and sides of the tank but all the way to the back. I don't think I put a screen between the crushed coral and the sand, but I'm not sure.

There are actually two reasons for the screen separating the top layer from the bottom layer. (1) The screen prevents burrowing animals from getting to the bottom layer and messing up the operation of your plenum system (because the bottom layer is supposed to remain undisturbed) and (2) if you placed "fine aragonite sand on top of crushed coral" the crushed coral will eventually rise to the top and the fine aragonite sand will settle to the bottom. That's just the way it works when you try to place a layer of finer particles over a layer of larger particles.

The test kits I used for the Mag and Alk are Salifert for the Alk and Seachem for the Mag.

I have experience with LaMotte's test kits for calcium and alkalinity and Salifert's test kits for just about everything else. I liked the LaMotte test kits. I sometimes had problems with some of the Salifert test kits.

In summary, it's quite possible that your recent problems with nuisance algae are the result of your recent plenum addition. It's also highly likely that you will have even worse problems down the road (two or three years from now) if you forgot to install the fine mesh screen to separate the two different layers.

You may find this article by Julian Sprung on the alleged advantages of a plenum system informative. Unfortunately, you will also learn that yours is not set up properly according to the advice he provides.

I will not discuss Julian's article other than to quote the following statement he made and offer my correction to it:

Author Ron Shimek is a proponent of the use of thick beds (25 cm or more) of fine sand without a plenum. He claims that such thick beds do not have a problem with hydrogen sulfide, and they function well for denitrification. I have not compared this method with Jaubert's.

In my humble opinion, that is a misrepresentation of what Dr. Ron Shimek has recommended for the past ten years or more. In particular, Dr. Shimek has said over the years that he considers the minimum depth for a deep sandbed to be 4" (10 cm). Julian makes it seem that Dr. Ron recommends a minimum depth of 25 cm or more. Julian doesn't agree with Dr. Ron on this topic, nor a lot of other topics. Ron has consistently said that the minimum depth should be 4" but that 6-8" would be better. Julian makes it seem that Ron is recommending a minimum of 10". There is nothing wrong with a 10" DSB. Julian believes there is and Ron believes there isn't. It's a long story.

P.S. -- When it comes to DSBs, you can find a wide variety of opinions of the minimum depth and optimal depth. As far as minimums are concerned, Ron recommends 4", another well respected author with a Ph.D. of his own recommends a minimum of 3" and another long-time author and hobbyist recommends a minimum of 8-10". IMHO, 3" could work in a relatively large aquarium but 4"-6" would provide more benefits. I guess it all depends on what you're trying to achieve. I see nothing wrong with 3" and nothing wrong with 5". I think 8" or more is for DSB fanatics who really are into DSBs. I have kept a 6" DSB with no problems whatsoever but I might be willing to go with something a little less in the future.

[shelleyo]

I saw Dr. Ron Shimek at a Reef convention in Oklahoma City last fall. He talked about the DSBs and although I don't remember exactly what he said about depth, the main thing he talk about was the organisms living in the sand beds. He said that if one had plenty of worms and such, they would turn the sandbeds over very regularly and they wouldn't have to worry about anarobic (?) spots in the sandbed. He very much recommended resupplying the sandbeds with worms and other animals who live in the sand on a regular basis. His talk was very interesting.

I may have to end up taking out the plenum. I just hate tearing up my tank, yet again, to do it.

[Ninong]

Originally Posted by shelleyo

He said that if one had plenty of worms and such, they would turn the sandbeds over very regularly and they wouldn't have to worry about anarobic (?) spots in the sandbed.

It's spelled anaerobic but he didn't say that. A deep sandbed wouldn't function properly if it didn't have both aerobic (oxic) and anaerobic (anoxic) areas.

He very much recommended resupplying the sandbeds with worms and other animals who live in the sand on a regular basis.

Yes, he definitely said that.

His talk was very interesting.

True.

I may have to end up taking out the plenum. I just hate tearing up my tank, yet again, to do it.

This is something you will have to think about because the longer you put it off, the worse it could be. Something for you to think about for a few days, weeks.

Check out these articles by Dr. Ron Shimek:

Muddy Waters

How Sand Beds Really Work

Check out these articles by Dr. Rob Toonen:

Are Plenums Obsolete? Part 1.

Are Plenums Obsolete? Part 2.

Don't be fooled by the titles, Rob's articles are not about plenums, they're about deep sand beds.

[shelleyo]

I just retested my mag and I am confused about how to read the results. This is with the Seachem Magnesium test. The instructions say:

"Fill the syringe with Magnesium Titrant to the 1mL (cc) level. Titrate with the syringe until the color turns from pink/magenta to blue. . . Read the volume of titrant used from the mL (cc) graduation.

In reading graduations from mL (cc) scale, note that the scale runs in reverse of dispensing, so that 0.9 = 125 mg/L; .0.8 = 250 mg/L . . . ; 0.2 = 1000 mg/L; 0.1 = 1125 mg/L; 0.0 = 1250 mg/L. Each line in between the graduations equals 12.5 mg/L. If magnesium exceeds 1250 mg/L (mg/L), it will be necessary to refill syringe and continue; add the volumes used from both syringe fills to get the total amount of titrant used."

Now, if I used .8 cc of titrant -- is my magnesium (the syringe plunger stopped at .2 cc) is my magnesium reading 250 mg/L or is it 1000 mg/L?

[Ninong]

I have never used that particular brand but it's obvious from the instructions that if you used 80% of the titration fluid in the titrator syringe and a full syringe equals 1250 mg/l Mg then your reading is 1000 mg/l Mg (1000 ppm). This is low but not critical. You need to raise it up to around 1300 ppm. I used ESV's B-Ionic Magnesium but you can even make your own magnesium additive if you feel like it. (P.S. -- I forgot to mention that you should increase your magnesium gradually over a period of several days at least. I would spread it out over ten days or so. There is no need to rush. Unless you are faced with a real emergency, there is never any real need to rush anything when it comes to changing water parameters.)

Magnesium in Reef Aquaria
http://www.advancedaquarist.com/issues/oct2003/chem.htm

[shelleyo]

Thanks a lot for your help, Ninong. I understand much better now and will start working on it.