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Discussion Starter · #1 ·
As the title implies I have had a small outbreak of GSA recently.

The tank is a 34 gallon with DIY light fixture made of 6500K screw in CFL's on for 8 hours and Pressurized CO2 injection 18 hours a day = constant 30ppm.

You can see it here: http://www.aquaticplantcentral.com/forumapc/journals/51372-logan-s-daddy-s-34-gallon.html

Nitrates have always been a little high so to maintain around 20 ppm I've cut the KNO3 dosing to half the "suggested" amount. I've also always had some problem with GSA on the older leaves and at this point I dose twice the "recommended" KH2PO4. This has been working for some time, but recently I've noticed a LOT of gsa on the leaves near the surface.





The leaves in the photo are only about a week old, also, it has almost completely covered most of my Ludwiga Glandulosa, even the new growth.

I'm really not sure what's causing it, Should I crank up the CO2? Add even more KH2PO4? Replace the Lightbulbs?

HELP!!
 

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When you decide to use the EI method of dosing you are accepting as facts that excess concentrations of nitrates, phosphates, etc. will not do any harm to the plants or fish. The whole method is built around that, and is intended for those who do no testing of nutrient concentration in the tank.

When you do test for nitrates, for example, you need to just look at the results as being of minor interest, but no importance, or you have to carefully calibrate the test kit. That means making water solutions with known ppm of nitrate in them, and using the test kit to make sure it reads that ppm accurately. (Or, you can make your own calibration table of color vs ppm instead of using the manufacturers table.)

Plants consume nitrates. They consume more nitrates than anything else in the water except CO2. So, it is difficult to maintain enough nitrates in the water to keep the plants non-limited by nitrates. Cutting back on dosing nitrates would only be a good idea if you were changing water every other day, and the change water had a high nitrate level from the tap, a very unlikely thing.

I suspect your GSA problem on leaves of a stem plant are caused by the plant's growth being inhibited by too little nitrate, making the leaves susceptible to algae attack. Algae doesn't grow on healthy growing leaves.
 

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Discussion Starter · #3 ·
Thanks for the quick reply Hoppy!
I always appreciate getting responses from you as your replies are generally no nonsense with accurate information backing them up.

As you can see in my signature pic my plant load is quite high ;) - do you think I should slightly increase all of the nutrients (above Tom's Baselines) to compensate?

Thanks again.
 

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From Tom Barr's forum I know that some people with heavily planted tanks do increase the EI dosages, sometimes to double the recommended amounts. Tom once told me those dosages are intended to be enough for even heavy planted tanks. So, I'm not sure whether increasing the dosage is a good idea or not.

One thing I am sure of is that when the tank gets really full of plant mass like that it slows down the water circulation in the tank a great deal. And, that can cause some plants to be starved for CO2 if not for other nutrients. I have learned the hard way that as beautiful as I find a tank that is really heavily planted, I always end up regretting not doing more pruning, after BBA starts growing all over the tank. Your tank doesn't seem to be quite as stuffed as I have let mine get, so you probably still have time to figure out what to prune to keep it from growing too much.

I always dose twice the EI recommended amount of phosphate to help control GSA, and it does help a lot. And, as to slightly increasing the dosages - don't bother, because they are such a crude estimate of the plants needs to start with, a 20% increase or decrease would probably not even be noticed by the plants. If you do increase them, just double them. The weekly 50% water changes will protect you from building up way too much of any of the fertilizers.
 

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What's your total light wattage? I had pretty bad GSA until I went from 4x54w T5's over my 72 gal down to 3.
 

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Discussion Starter · #6 ·
Currently running 5 23W CFL's - you can see the setup in my signature thread, 115 total watts over a 34 gallon tank would be about 3.3 wpg, BUT, I lose a lot of light to restrike due to the design of the bulbs, I estimate they are about 60 - 70 percent as efficient as a T-5 setup with the same wattage, giving me an effective 2-2.5 WPG.

This is the same setup that I've run for over a year with no issues until the last few weeks.

Do you think it could be the fact that the bulbs are getting old?
 

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It's due to a lack of CO2. It's not so much that you aren't injecting enough, it's because it's not circulating properly. I've been carefully observing this for the past year, and every time I get a little GSA on leaves, it always shows up when circulation diminishes. The higher the lighting, the tighter the tolerances. Getting the nutrients right is relatively easy, but the proper use of CO2 is far more difficult. Focus on keeping plants pruned regularly so as not to obstruct flow and be sure there is adequate, even flow throughout every part of the tank. It's not necessary to run high light if your CO2 can hit on all cylinders. It may take longer for plants to grow, but they will grow with exceptional health and coloration. It will also give you more time to observe and make adjustments.
 
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