h202 question. please help - The Planted Tank Forum
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post #1 of 4 (permalink) Old 09-17-2014, 07:30 AM Thread Starter
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h202 question. please help

I know h202 will degrade fairly quickly in an aquarium. I also know it can harm beneficial bacteria. I use it to spot treat algae in my planted tank. I turn off all filters and flow when spot treating. How long does it take for the h202 to do its job and degrade to a point of being non harmful to the beneficial bacteria , to be able to turn my filters back on. Or is this something I shouldn't be concerned about?

55 gal tank
Pressurized co2
Pps fert dosing / excel dosed daily
48 inch finnex planted plus
2 aquaclear hob filters

Last edited by rick dale; 01-11-2015 at 05:46 PM.
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post #2 of 4 (permalink) Old 09-17-2014, 08:07 AM
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Depends on how much H2O2 you use, how much organic material (the gentry call it TOC) there is in the water and how well established your aquarium is.

What is a perfectly harmless dose one day can be lethal the next.

Generally Hydrogen peroxide works quickly and aggressively, it is in fact more aggressive than household bleach.

In a 55-gallon aquarium staying around 40-ml of 3% H2O2 (about 7-ppm H2O2) in a 6-hour period should be conservative. I tend to be a good bit more aggressive, if you are dosing frequently, it is best to be conservative.

Since you have the algae that is a good indication you have elevated total organic carbon (TOC), so in addition to attacking the alga directly you are oxidizing the excess organic carbon, the problem is that once the undesirable organic carbon is gone, the gills of your fish are handy targets.

So the overall answer is to reduce the dissolved organic carbon load, the usual suspects are over feeding and dirty or overloaded filters.

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post #3 of 4 (permalink) Old 09-17-2014, 11:43 AM Thread Starter
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Thanks for the info. I only feed what the fish eat . I try to not let any go to the sub. I do probably need to clean my filters more often. That could be part of the problem.
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post #4 of 4 (permalink) Old 09-17-2014, 01:34 PM
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If the total amount you are adding (while the filters are off) is not more than the total amount that is generally safe for your tank, then it will be OK when you turn the filters back on because some of it is danatured pretty fast (all that bubbling). So what is left is well under the safe level.

As to how fast it will break apart, it depends on several things, but a safe, conservative approach is to wait 24 hours, and do a 50% water change before re-dosing. This would allow plenty of time for it to break down, and remove a lot of it so you know it is well into the safe zone even when you re-dose.
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