# Question on MDC method



## johnzhou2476 (Nov 28, 2006)

I've just spent two hours reading on the MDC method sticky. This sounds too good to be true. It seems that with EI, I always get GDA due to my high wpg and high phosphate level. Christian claim that the only time he had to reduce his light output was when he was running at 12wpg. That's insane! 

Has anyone tried this method? Does this mean that I can run high wpg as long as I keep my phosphate at around .5 ppm and nitrate below 5ppm, also inverse the calcium and mg ratio, meaning higher mg to ca ratio. I want explosive growth without algae and this sounds too good to be true. I have pressurized co2, so I should have no problem keeping my co2 level high.


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## armedbiggiet (May 6, 2006)

it is all depenting on what are you going to plant and whta type of the plants. If you are going to have phosphate in it make sure your plants are fast phosphate eater as you think you undersatnd and figure out how much phosphate you have in your tank but do you know how much and fast do what ever your plants put in would eat up before your algae had a chace? If you want it fast in a very short time and very few algae problem... high CO2 + strong lights(WPG is not a good way to count) and do water change 30% of the tank everyday. I did that cause of my discus and shrimps breeding.


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## bosmahe1 (May 14, 2005)

johnzhou2476 said:


> I've just spent two hours reading on the MDC method sticky. This sounds too good to be true. It seems that with EI, I always get GDA due to my high wpg and high phosphate level. Christian claim that the only time he had to reduce his light output was when he was running at 12wpg. That's insane!
> 
> Has anyone tried this method? Does this mean that I can run high wpg as long as I keep my phosphate at around .5 ppm and nitrate below 5ppm, also inverse the calcium and mg ratio, meaning higher mg to ca ratio. I want explosive growth without algae and this sounds too good to be true. I have pressurized co2, so I should have no problem keeping my co2 level high.


I personally would never get to GSA with the MDC method. That's with 156 watts T5 HO over 46 gallons of water. That's probably because it isn't quite 1 watt per Liter. I have reduced phosphate dosing to .7 ppm and found in my case, that the high phosphate dosing of EI isn't necessary. I do adhere to the 50 % water changes now and it seems to reduce my GDA considerably. I used to do 30 % twice a week, the 50 % once per week seems to work better for me. My KNO3 dosing amount is close to EI but I divide it into daily dosing.


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## johnzhou2476 (Nov 28, 2006)

Very interesting - I'm curious as to why water change every day helps so much? I know the idea of massive water change is to reset everything but I've also read that under EI method, Nitrate level can be anywhere from 5ppm to 20ppm. That's a huge range. So even without water change everyday, you would still be within that target range. So that being the case, how would water change everyday optimize growth? I must be missing something....

One more question, my tap water is super soft. I check my TDS and it's around 40ppm. Both GH and KH is less than 1 degree. If I do water change everday, does that also mean I have to raise my GH everyday?


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## bosmahe1 (May 14, 2005)

Sorry, I meant 50 % water change per week vs. 2 x 30 % water change seemed to improve things. I guess 2x30s don't reset as well as 1x50% (makes sense). I suppose something was out of balance and was better reset with the 50. I gave up trusting test kits, especially ones for nitrogen, so I can't elaborate on what truly changed. Total hardness is 100 ppm as quoted from water company.


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## DVS (Nov 20, 2005)

If you believe that excess nutrients (especially phosphate) results in nuisance algae, then this seems like a great method. Not to deride the work that was put into this but I'm having a difficult time really differentiating from Sears-Conlin.


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## bosmahe1 (May 14, 2005)

DVS said:


> If you believe that excess nutrients (especially phosphate) results in nuisance algae, then this seems like a great method. Not to deride the work that was put into this but I'm having a difficult time really differentiating from Sears-Conlin.


If I remember correctly, Sears-Conlin's idea was to eliminate phosphate to put algae at a disadvantage. The MDC (as I understand it) uses nitrate in increasing amounts, to find its set point which is determined by Green Spot Algae appearing. Once GSA appears, you add phosphate in increasing amounts to eliminate GSA. Sears-Conlin doesn't work since algae can thrive on less nutrients including phosphate, than plants need. So far, MDC hasn't worked for me, maybe because I don't have 1 watt per liter. What has improved things for me is increasing water changes, as suggested by EI. Why, I don't know.  I am still adding KNO3 and CSM+B in excess between water changes. I don't add phosphate in the same amounts as EI anymore. But, I don't think that has made a difference, either way.


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## DVS (Nov 20, 2005)

From the first paragraph of the recommendation section of Sears-Conlin:



> Plants cannot grow without phosphate. However, in order to keep a planted aquarium relatively algae free, free phosphate in the water column must be minimized.


The paper does theorize that eliminating the phosphates from the water column would be the ultimate goal with phosphate provided by a fortified substrate.

I've read throught the MDC threads and I will admit I think the language barrier may have me a little confused on a few points, but my understanding is the method is used to develop some level of "correct dosing" that will leave no "extra" nutrients in the water to fuel algae growth. I believe its suggested .5 ppm of phosphate is adequate. Definitely a leaner tank then many methods recommend.


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## bosmahe1 (May 14, 2005)

With sufficient light, algae will thrive in nutrient levels not sufficient for plant growth. If you are trying to grow plants, starving algae isn't really possible. Nobody really follows Sears-Conlin anymore. The MDC is trying to find the balance needed in your particular tank, it's not really limiting anything. MDC doesn't work for me but, it made me realize I don't need to dump 2 ppm of phosphate into the tank. I shoot for .7 ppm. Does it help with algae? No not really, I just reduced to .7 ppm because 2 ppm seems unnecessary. I used to have a 20 gallon tank that had aquatic soil that I bought at Home Depot. For some reason, it stayed at 6 ppm phosphate for over a year. Did it have more algae than my 46 gallon? No, just different kinds. Depending on how your lighting - nutrient - Co2 - plant population levels are, it will favor one type of algae over others. It's all a balancing act. That's why it is so hard to find one method that works for everybody. Another thing that makes it hard is, when your co2 level especially, but also if anything else changes in balance, It tends to trigger algae blooms, for whatever algae prefers that environment. People might make big changes based on something they read and boom, algae explosion. It is hard to have the patience to do things gradually enough to improve things. Because in the mean time, you will plucking algae and trimming off infested plants thinking, this isn't working either.

I'm certainly no expert at this, I'm just now starting to win my 2 year battle with Black Beard Algae.  It was like they have always said, it was related to current and co2 levels. My co2 levels have been good for quite some time, but it took all this time for me to adjust my water flow in the right way. I also altered my water changes. It seems I'm having better luck doing at least one 50% water change weekly, than doing two 30 % water changes.

In closing, you can't eliminate algae by eliminating nutrients. You have to try to find the balance that favors your plants vs. algae.


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## ashappard (Jun 3, 2006)

bosmahe1 said:


> Nobody really follows Sears-Conlin anymore.


true, but it comes up often enough still today. The value in these old papers is usually in the common sense knowledge they contain, plants need available nutrients etc. Levels of macros and traces are debatable and vary between spp. What they seem to leave out is the importance of CO2 and flow, especially in high light aquariums on an extended timeline.

where CO2 and flow are good, then nutrients become important. The plants will consume them more rapidly and avoiding limitation is trickier. Mixing spp together in a tank that prefer different ranges also makes the work more difficult and again these papers are no help there. Sears Conlin for example focused on incredibly easy species of plants, which will grow acceptably in a _very wide_ range of parameters. I've seen other papers used as reference that focus on Hydrilla! you can grow that stuff on your old bathwater.

Water changes in high light tanks are handy when it comes to maintaining levels of nutrients, avoiding buildup and keeping ratios in check. They also promote cleanliness, and a general hands-on approach to husbandry. If you pull out some water, trim and clean up, then add water back in and then continue dosing - you are more likely to maintain balance and disrupt the ability of algae to become established. At least my experience follows that pattern. When light is strong, I notice that cleanliness / CO2 and flow are most important to manage -- when I slide on that, it doesn't matter how fancy my dosing method is, I'll end up with instability. When the tank is clean and no stagnant areas exist, I can get by with very simple dosing methods. Pretty much any method will do.


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## DVS (Nov 20, 2005)

bosmahe1 said:


> With sufficient light, algae will thrive in nutrient levels not sufficient for plant growth. If you are trying to grow plants, starving algae isn't really possible.


Agree totally.



bosmahe1 said:


> Nobody really follows Sears-Conlin anymore.


Depends on how you look at it. Sears-Conlin suggested dosing all nutrients (including light) in excess of available phosphate. Most don't try this any more. Most popular fertilizer regimens now dose nutrients in a slight excess of available light. Really we just changed the limiting nutrient. That may kind of be a weird way of looking at it but I never professed to be normal.  I kind of think of Sears-Conlin as an important step to where we are now.



bosmahe1 said:


> The MDC is trying to find the balance needed in your particular tank, it's not really limiting anything. MDC doesn't work for me but, it made me realize I don't need to dump 2 ppm of phosphate into the tank. I shoot for .7 ppm. Does it help with algae? No not really, I just reduced to .7 ppm because 2 ppm seems unnecessary.


Total agreement with you. But, I do believe that MDC at least insinuates that 2 ppm of PO4 is going to cause an algae problem if not wouldn't doing EI and reducing levels to whats needed be a little more straight forward. For the price of dry ferts why worry about it. I will say .7 ppm is pretty lean, my concern would be natural fluctuations in plant uptake based on mass etc., or test kit error leading to nutrient shortages and resulting problems.



bosmahe1 said:


> I used to have a 20 gallon tank that had aquatic soil that I bought at Home Depot. For some reason, it stayed at 6 ppm phosphate for over a year. Did it have more algae than my 46 gallon? No, just different kinds. Depending on how your lighting - nutrient - Co2 - plant population levels are, it will favor one type of algae over others. It's all a balancing act. That's why it is so hard to find one method that works for everybody. Another thing that makes it hard is, when your co2 level especially, but also if anything else changes in balance, It tends to trigger algae blooms, for whatever algae prefers that environment.


I think you are essentially saying the same as my previous point and it would be my concern when running narrow excesses.



bosmahe1 said:


> People might make big changes based on something they read and boom, algae explosion. It is hard to have the patience to do things gradually enough to improve things. Because in the mean time, you will plucking algae and trimming off infested plants thinking, this isn't working either.


I notice this alot too. Its funny when I see a post, I've been doing X for 2 days and it can't work because things have not improved or gotten worse.



bosmahe1 said:


> I'm certainly no expert at this, .


Quite possibly closer to being an expert then me.



bosmahe1 said:


> I'm just now starting to win my 2 year battle with Black Beard Algae.


I think this is the big one. Once you beat BBA everything else is relatively simple (IMO). If you are doing DIY CO2 you have to be right on top of it all the time. I'm in the same boat and I think recent successes are due to going pressurized.



bosmahe1 said:


> In closing, you can't eliminate algae by eliminating nutrients.


j\

Now your just preaching to the choir  I get confused when someone seems to insinuate that .7ppm of phosphate is fine but 1.5 ppm will cause algae which is what I'm getting from MDC but I'm probably of base.


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## DVS (Nov 20, 2005)

BTW, just so I'm clear. I believe the method could be effective and I applaud the effort in coming up with it. People don't seem to put the effort into experimentation and reporting that was prevalent in the Sears-Conlin era. Alot of people today don't seem to believe that plants can be grown with cool white t-12s.


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## bosmahe1 (May 14, 2005)

When I started with plants 4 years ago, I studied Sears - Conlin on an almost daily basis. They sure taught me alot. Only problem was when I had hair algae, I immediately ran to the LFS looking for a phosphate filter pad. Funny, it didn't help . I've been running pressurized for about 2 years now, with bubble ladders, ceramic diffusers, PVC inline reactors, pumped into canister intake, pumped into in tank waterpump and for the same 2 years fought BBA. I wouldn't get BBA on the plants so, I knew the fert regimen was at least good for the plants. I just couldn't keep it off of the gravel or plumbing. Even with lime green 4 kdh drop checker. Letting the drop checker turn yellow didn't help in this case either. My last mistake in the fight was to aim the waterpump towards the gravel, co2 bubbles everywhere and plants pearling like crazy. I was dumb founded because, I would find bba attached to the gravel everyday. I would suck out the infected flourite everytime I did a water change. I thought I would have to buy more flourite soon. I then decided to try one of those $5.00 Asian inline diffusers against my better judgement. I bought two because the shipping was more expensive than the diffusers. I put the diffuser on the output of my Rena XP2 and removed the spray bar, moving the output flow away from the gravel and removed the water pump. Now I get very very little BBA. I decided to try one 50 % water change per week instead of two 30 % and now I get less Green Dust Algae as well. Alot of these changes came about over months. I went down the road applying all of the suggestions about co2, flow, misting, nutrients, light duration, plant load etc... and it wasn't any one thing that solved the problem. It was some wierd combination that I hit on by chance. Good thing though, now I have a formula that works so I can do just minor tweaks and observe. Why it took two years, who knows, calcium-magnesium imbalance? The only way would be to try this all again with RO, naaaaaaa!!!!


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## ashappard (Jun 3, 2006)

DVS said:


> People don't seem to put the effort into experimentation and reporting that was prevalent in the Sears-Conlin era. Alot of people today don't seem to believe that plants can be grown with cool white t-12s.


Maybe its not so much that plants can't grow with T12s as much as the efficiency that newer lighting systems provide. Light is light when you boil it down, but efficiency = $/yield/space if you bother with that stuff.

and as far as experimentation and reporting on methods, I think its active today as much as yesterday. The hobby has grown, and a lot has been learned in regards to methods. The acquisition of new spp. largely drives the improvement of methods in my opinion, the science catches up at some point.


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