Blackout Method - Anyone try it? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 10 Old 04-22-2008, 07:04 PM Thread Starter
Blackout Method - Anyone try it?

Has anyone tried the blackout method for eliminating green water and how did your fish and plants fare in this process?

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post #2 of 10 Old 04-22-2008, 07:24 PM
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Not only have i tried it, i have used the technique dozens of times for other fishkeepers. The basic idea is to turn off the light and cover the aquarium with a sheet. You want total darkness. The green water dies off from lack of light. This method should not be used on live plant aquariums or on marine systems. Additionally, you must test the water several times per day and monitor the biological filtration process during treatment to avoid ammonia spikes. For this reason, a blackout should only be used on established aquariums.

There are a lot of things to be cautious about when using this technique. First, and VERY important, you need to know the cause of the green water. Green water is a big indicator that there are problems within the system.

I would feel much more comfortable if we could first diagnose the aquarium and then treat for green water. Can you post test results for Ammonia, Nitrite, and pH? How often do you change water? How do you condition the water? What types of light bulbs do you have and how old are they? How long has your aquarium been set up? What size tank and what livestock?
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post #3 of 10 Old 04-22-2008, 07:30 PM
Blackout should be a last resort only
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post #4 of 10 Old 04-22-2008, 11:51 PM Thread Starter
Tank Information

OK, here is my current situation:
20 Gal long tank, cycled and established since last October. Weekly water changes 4 gallons or so. Gravel vac weekly as part of water change. Homemade coil denitrator that moves about 1/2 gal per hour.

Inhabitants: 6 neons, 2 adult red wags, a half dozen fry, two serpae tetra, two large flat silver tetra (yeah, I don't know what they are called), two very tiny algae eating catfish and one large chinese algea eater.

Normal readings:
Ammon: 0
Nitrite: 0
Nitrate: 0 - 5 ppm
Phosphate: 10+ ppm
ph ranges from 7.2 to almost 8 if I don't keep after it.
API liquid test kits.

I've been battling ph since the beginning as a result of my tap water having some strange properties that makes it go very high after about 24 hours of aeration. I've posted about this previously. Until March I was using neutral regulator which is loaded with phosphates. I didn't know this and suspect this contributed to my problems with ph because dosing with neutral regulator did not appear to get me near to 7.0. I've also had lots of algae with Seachem told me was because of the phosphates.

Fast forward to mid March. I did something really stupid that killed the biological filter in my Aquaclear 30 filter. I added acid buffer directly to the intake, hoping it would disperse into the water gently. Yeah, I know, don't say it - duh! Acid water kills bacteria.

On April 6th I observed cloudy water and measured Ammonia at 1.0 for the first time ever. I treated the water with AmQuel and Stresszyme and changed 5 gallons each day for a few days. Then the algae bloom appeared.

Since then it has been perpetually green. I assume the algae got started on the ammonia and then ran wild. I turned off most of the lights but it continued to stay green. That's when I started looking for non-chemical ways to fix it. I used to get algae on the walls and plants. Since the green bloom the algae on the surfaces of things has stopped so clearly the green water is eating the food the other stuff was enjoying.

Ammonia went down to below 0.25 ppm and then dissapeared after the Amquel dose (just one) and the green appeared. That was on 4/7. By 4/10 the readings were all back to zero except phosphate which is always north of 10+

Last night I purchased a Marineland 350 canister filter with micron cartridge and set it up. Over night nothing got better but today when I got home it had started to polish out the green in the water and I could actually see the fish again. I vacuumed the gravel again and moved some ornaments around to clean under them. I have new babies again from the Red wags so I could not get too agressive but I took a lot of debris and dead stuff out. Remember I have a number of live plants also and I had some leaves and stuff on the bottom from the reduced light. Overall the plants seem pretty good and I have been dosing with Flourish Excel all through the green cycle.

Current readings:
Ammonia: 0+ (below 0.25, no color change)
Nitrite: 0
Nitrate: 2.5
Phosphate: 10+
ph 7.2

I looks like my denitrator is not working, maybe I hurt it also with the cycle but I won't react to that for a while as touching it means many months for it to establish again. It seemed to always keep my nitrates at 0+ but less than 2.5 for the last many months.

OK, thants all my info, let me know what you think or what else I need to tell you.
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post #5 of 10 Old 04-23-2008, 05:57 AM
You need nitrates in your tank and I think sometimes lower nitrates like that actually contribute to an algae problem, anything up to 20 is ok. Plus, you might want to stop with the chemicals, it can make a problem worse. 8 isn't horribly high for pH and most fish can adjust, plus you can try to filter over peat for a more natural solution. Sounds like the filter is helping.
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post #6 of 10 Old 04-23-2008, 09:45 AM Thread Starter
Originally Posted by Flashygrrl
You need nitrates in your tank and I think sometimes lower nitrates like that actually contribute to an algae problem, anything up to 20 is ok. Plus, you might want to stop with the chemicals, it can make a problem worse. 8 isn't horribly high for pH and most fish can adjust, plus you can try to filter over peat for a more natural solution. Sounds like the filter is helping.
Thanks for the thoughts. I have found that if the ph gets above about 7.6 the tetras get really stressed, stop eating, and in the case of my neons they seem to stroke out and die. I was losing neons at a saddening pace until I got the ph lower. I'm sure it is a mixture of one thing plus another plus another, not just ph by itself.

I am very interested in your thoughts on nitrates. When the tank first cycled and was getting established I had nitrates in the 40 - 80 range. That's when I was doing larger water changes and started the denitrator running. It has worked very well. What range do you target for nitrates and how do you control them? I thought most people here we trying to stay below 5 ppm rather than 20 but 20 would be much easier to maintain.
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post #7 of 10 Old 04-23-2008, 11:26 AM
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That's odd with the tetras not liking the higher pH. I had them in a tnak with mystery snails and kept my pH at 7.6-8.2. There may be another reason for that. If your KH is too low then the pH swings could be cauisng the problem and not the levels themselves. A KH of 3 is recommended for any tank to help prevent major osmotic problems with fish in general.

As for nitrates and phosphates, the ratio is off. It should be closer to 10:1 nitrates:phosphates. Having low nitrates is not bad and won't really cause algae but a bad ration will. I even know plant keepers who deliberately keep Nitrates under 5ppm to bring out reds and oranges in their plants.

Water changes will eventually get your phosphates down as will feeding a little less. Fish Food is the biggest cause of high phosphates as is tap water sometimes.

As for blackouts, I have done them on a planted tank without much problem. The plants wimpered and moped for a week or so but no real harm. Also, when doing a blackout, You can not open the tnak for any reason during the entire 3 days. Any light will feed the green water just enough that will simply come back in a week or two. Get your tank balanced and for the most part green water is not a problem. Unless you have my tanks that simply like to "Go Green". lol
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post #8 of 10 Old 04-23-2008, 11:44 AM Thread Starter

My tap water tests at 5.0 ppm phosphates. That means the best I could ever get to is 5, right? I am sure I am still diluting down the phosphate level from when I was using the Neutral Regulator. Phosphates hide in glass and in stone so I may be leaching them back out for ever.

Did you say my ratio of phosphate to nitrate should 10:1, i.e. if my nitrate is 10 ppm my phosphate should be 1.0 ppm?

Is there anything that will neutralize the phosphates other than water changes, since my water is 5.0 anyway?
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post #9 of 10 Old 04-23-2008, 01:19 PM
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I wish I knew of something that absorbed PO4 but I have never used one so I can't recommend anything.

Plants will use them up. Elodea/Anacharis is often used to take up excess nutrients.
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post #10 of 10 Old 04-23-2008, 06:02 PM
Water lettuce is very effective as well- it floats on top and the roots drink up everything. I've got some friends who call them "nitrate eliminators"
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