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PMDD - plenty of data available but how much to dose??
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Hjalti
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Joined: 25 Sep 2003
Location: Reykjavik, Iceland

PostPosted: 2007.01.01(Mon)10:51    Post subject: PMDD - plenty of data available but how much to dose?? Reply with quote

Hey,
So I have been trying out PMDD for over a year now. I base my mix on the data available from the internet but I still find it very difficult to find instructions on how MUCH to dose. I would be very glad to get some suggestions as to dosing quantities.

My tank is 820L with 450W MH lighting and a CO2 tank. I still find it very difficult to get my CO2 up to the 20-30ppm range and mine lingers at around 10ppm. I do 10% water changes every week.

Assuming I am using a mix in the typical concentrations as explained for instance on the following web site:
http://www.thekrib.com/Plants/Fertilizer/pmdd-tim.html
(my mix is different but it is still roughly in these concentrations, mixed in 0,5L.)

My question is, giving the above, how should I dose. Daily, weekly? and how much. I am currently dosing 5-6ml per day and am basing that on something I found on the web but I seriously have no idea if that's the way to do it, in fact, I quite doubt it. My plants have been growing ridiculously fast but are still quite pale looking and not "bubbly" looking.

And just to note, don't point me to the estimative index method. There is absolutely no way I can change more than 10% of the water per week.

I would be very grateful to get some tips on this!
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ngocthach1130
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Joined: 23 Oct 2006

PostPosted: 2007.01.02(Tue)2:41    Post subject: Reply with quote

check http://www.rexgrigg.com/ the nutrient section. I think he specify how much the level should be for those and also said it's done 3x per week I think
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silenoz
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Joined: 09 Aug 2006
Location: Davis, CA

PostPosted: 2007.01.02(Tue)11:22    Post subject: Reply with quote

wow, thats a big tank. I admire your bravery. my reply in related to your CO2 level in the tank. What type of setup do you have, I assume its pressurized, but what are you using to diffuse it into the tank??? If you aren't using an inline reactor a-la Rex Griggs, I highly recommend you do so, it bumped my ppm from about 7 to 22. I don't have anything to offer on the PMDD front, I buy individual ferts from Gregg Watson and dose as needed, but I agree that Rex's site will probably help, if not then PM him.
Good luck
Peace
~silenoz
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Plantbrain
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Joined: 10 Dec 2003
Location: The swamp

PostPosted: 2007.01.03(Wed)11:48    Post subject: Reply with quote

You will have many issues until you address the CO2.
You really need to work on that much more than PMDD.

PMDD was developed using very low light, about 1/2 the lighting you have (MH's are much better than older standard FL's tubes).
Obviously, you will have more CO2 demand with more light since light drives CO2 uptake rates.

So the downstream uptake of NO3, NH4, Fe, K+ etc, will be hampered as a result.

Algae like variable CO2 and low CO2 under high light, which is what you have.

You need more current to mix the CO2 well in larger tanks.
You can use a venturi in line, fed the CO2 into ther suction side of the filter return pump, etc, add glass diffusers(see ebay's Rhinox type, very good for the $$).

I'd use no less than 2 diffusers or 1-2 venturi's.You can also make a CO2 reactor DIY, I'd use two, not one and make sure you have at least 300-400 gph going through each of them.

That will address the low CO2.
Adjust the CO2 slowly and raise it up with care looking at the fish and the plant health.

See the KH reference solution drop checker thread(doa google search for it) for a nice little test method that works well for CO2.

FYI, most have since rejected the hypothesis that PMDD was based on as it was easily falsified by myself and then most anyone with common sense about 10 years ago. Most have moved to EI which adds more CO2, more NO3, a lot more PO4 and requires no test kits. If you use the drop checker, then that is the only thing you need to watch along with the plants if you use that and EI. No testing at all. Ever.

You can search EI my name and should come up with many hits.

Regards,
Tom Barr
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Hjalti
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Joined: 25 Sep 2003
Location: Reykjavik, Iceland

PostPosted: 2007.01.08(Mon)18:12    Post subject: Reply with quote

Thanks for the feedback. Especially the lengthy response Tom. But the estimative index, isn't the whole theory based on doing 50% water changes every week and only in so doing can you get away with dosing so many nutrients. How do I avoid substance accumulation in the tank, seeing as the dosage is never going to be perfect? There is no way I am changing more than 10% of the water every week and have to adapt my techniaue to that.

As for the diffuser (I assume you're referring to the reactor), I am using the aquamedic 1000 reactor and the pump has an output of 1900L/h. Once the bubbles enter the tank, they get trapped in the roots of my surface plants yet my CO2 does not exceed 10ppm. There is hardly any surface agitation. Granted I am only diffusing a few drops per second but somehow am reluctant to go higher as it's a bit chilly in the winter (meaning it's not very practical to keep all windows open) and don't want to get excessive CO2 levels in my apartment Smile
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Plantbrain
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Joined: 10 Dec 2003
Location: The swamp

PostPosted: 2007.01.09(Tue)0:06    Post subject: Reply with quote

Hjalti wrote:
Thanks for the feedback. Especially the lengthy response Tom. But the estimative index, isn't the whole theory based on doing 50% water changes every week and only in so doing can you get away with dosing so many nutrients. How do I avoid substance accumulation in the tank, seeing as the dosage is never going to be perfect? There is no way I am changing more than 10% of the water every week and have to adapt my techniaue to that.


Then go non CO2 or plan on doing a lot of testing, there's a trade off for not doing water changes, either slow growth, balanced non CO2 approaches, or lots of testing.

There are grades in between though, EI is not written in stone that you must do 50% weekly changes, I've extended it out to two weeks etc, but I do larger changes then and have a good feel for the test's uptake rates so I can guess the ppms easily.
Obviously if you do larger and more frequent changes, the accuracy of EI increases, if you reduce the % and time between, the accuracy declines.

Some find a nice balance for their tanks in there.
But that will not be done unless you address the CO2 first and foremost.

Large tanks are easy to change if you use a python type system or a larger tubing modified. Check into this since it'll save you lots of time.

I use ball valves and large hose, takes me 20 minutes to drain a 1600 gallon tank (800 gallons) and about 2 hours to fill. I trim and prune while the tank drains and fills.

I have a 350 that I do a similar routine.
About 1.5 hours or so but it has a smaller refill hose.
I did 6 tanks in my old small place, about 160 gallon on my lunch hour.
I'd prune the day/night before and then do the water changes.
The draining was with a bucket there also, the filling was with a hose attached to the bath.

The problem with testing, I've never met a single person that keeps up on their testing habits over time. They do it after there is an issue, not much on preventative habits.
I think some think they can see the nutrients in the water, but without testing a lot and moving the nutrients around in controlled manner, you will have trouble relating plant issues with nutrient issues. That takes a lot of testing and experience.

Quote:

As for the diffuser (I assume you're referring to the reactor), I am using the aquamedic 1000 reactor and the pump has an output of 1900L/h. Once the bubbles enter the tank, they get trapped in the roots of my surface plants yet my CO2 does not exceed 10ppm. There is hardly any surface agitation. Granted I am only diffusing a few drops per second but somehow am reluctant to go higher as it's a bit chilly in the winter (meaning it's not very practical to keep all windows open) and don't want to get excessive CO2 levels in my apartment Smile


That's not enough for this tank, you need 2x this and at least 400 gph powerheads driving them.

CO2 in your apratment? Laughing
Haha, better stop breathing then and take out that trash, not farts either:)
Sorry to laugh, I know you are likely serious, but that's a new one on me.

You should not worry nor fear such things, CO2 is quite another matterm, but CO2 is fine , the place has venting, no place is sealed air tight and this should never be a concern.

I've had a lot more tanks and gas running and I only twitch a bit in the morning when the light hits me just right Cool

Regards,
Tom Barr
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