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[APD] Re: Algae fix

I have a 75 gallon tank with 2 175 watt metal halide pendants that has been set up for 9 months. It has Flourite/Onyx substrate with about 2 cups of peat mixed in the lower layer. I was dosing with PMDD, then Flourish and Flourish Trace, and now I am back to PMDD. My Tank has been very sensative to any changes, and even trimming my stand of bacopa has helped to kick off a plague hair algae or BGA. Some further tank stats are PH 6.6, 4ºKH, 2ºGH, pressurized CO2, Eheim Pro 2224, and an assortment of plants. I have tried dosing with Tom Barr's method and I was not very successful, because I kept loosing track of when to dose. I went back to dosing daily, so that way I do not forget. Now on to my delema...

I've seen this post somewhere, maybe the post all fuse together:)

"My tap water contains .52 mg/l of Zinc, 3.6 mg/l phosphate, 25.3 mg/l sodium, 9 mg/l sulfate, and 40 mg/l chloride. The other minerals are not very high, but still I have to pre-filter the tap water through carbon and a phosphate reducing resin before adding it to my tank. "

Have to filter?
Err why?

"When I change 10 gallons and I filter, then I am usually good to go, but if I have to change out 20 gallons, I am sure to get an outbreak of BGA. "

Well this means you need more KNO3 most likely. In any event, adding it will help this tank. What are the NO3's from the tap?

I suspecty the larger water changes adds more PO4/Zn and CO2 so the plants grow faster, and remove all the NO3/NH4. 

Under those conditions, BGA likes to thrive.
Call and see what the tap's NO3 is. PO4 is fine, you can do 50% weekly water changes and have enough PO4 for the week, PO4 does not cause algae. You are using CO2 and have a NO3 limited tank most likely, so adding more PO4 is not going to cause any algae................ 

"I am under the impression that using reverse osmosis water will help me to keep a good balance, and avoid some of the guess work."

And complicate things/give you more work to do. I have only heard of two rare cases, one with gasoline and the other with very high Copper and one more with very high sodium and Chloride levels that needed RO.

Generally RO is simply not needed for planted tank plants, the fish might be a different story, but you do not need it for the plants.

" On the other hand I could also switch the lights out for compact flourescents and not have such a sensative system. I have been able to keep the tank teetering on the line between luxuriant growth, and hair algae or bga outbreak. I was able to keep one of my metal halide pendants on my 29 gallon tank for about 5 months before I got a larger tank. The 29g had compact florescent lighting and was growing not half bad, but once the MH pendant was installed, the growth exploded and the tank was so thick with growth, and I REALLY want to duplicate this. 
Can someone share some of their experiences or knowledge with me regarding what would be better. I have the option of either getting an RO unit or Compact Flourescent lighting for christmas and although I would rather keep my MH lighting, I want to make the most informed decission. I was also considering getting a good test kit, but I have all the Hagen test kits for fresh water and they seem to work OK and match the city's water tests, with exception of PO4 which varies daily between 2-4 mg/l. What do you think?"

Well save the $ and do not buy the test kits. I really don't think light is so much the issue(you have 2w/gal or more?), it's nutrients and CO2 99% of the time. Get the PC lights if you want.

If daily works better for you, try this:
add 1-1.5 teaspoons of KNO3 and dilute in 70 mls of water, dose 10 mls a day.
Add K2SO4 after water change only.
Do not add KH2PO4, use the Tap water
Add traces, 6mls a day

So you are adding only two things daily, traces and KNO3.

You might want to add a little CaCO3 or CaCl2 and MgSO4(Epsom salt) after the water change, say 1/2 teaspoon of Ca and 1/4 of the Mg.

That should be an easy routine and the ratios and volumes are all worked out there for you.
I'd stay at 220w if you do go ahead with the PC light.

Tom Barr


Thank you

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