This came up in discussion in my tank journal; I'm posting some information I got from Tom Barr several months back that helped me to overcome a nasty algae infestation. Tom has two methods for dealing with it, depending on whether the tank is CO2-enriched or not. These directions were for a non-CO2 tank. The blackout instructions were common to both methods, and I found, very effective. It killed the algae but the plants and fish were just fine. I was pretty frustrated at the point when I did this, and was ready to tear the tank down if necessary to get rid of the plague. I highly recommend the blackout method as a way of getting a new start. It worked for me.
Blackout
Prune unhealthy or heavily infested leaves, scrape algae and clean the tank. If a lot of plants have to be removed due to severity of the infestation, replace with new. Clean out your filter. Do a 50% water change. Cover the tank with something to block out the light and turn off the lights for 3-5 days. Turn off the CO2 also and drop an airstone in the tank. Now sit on your hands (I did mine on a Thursday and left for a long weekend on Friday- not as nerve-wracking that way).
Uncover the tank. Do another 50% water change.
Post-blackout changes
This is partly specific to my tank, so only applies in principle to any other tank.
Original setup: 20xh tank (24" deep), 1.5wpg NO lighting (2 15w tubes), KH 7, DIY CO2 around 20ppm, Onyx/Flourite/gravel substrate, slow growing plants (Crypts and Anubias)
I decided to chuck the CO2, and this is Tom's response verbatim:
"No, CO2? Now things/method need to change. Do not mix these two methods(CO2 vs non CO2/carbon enriched) together.
You might try using Excel, but you may as well use CO2 then.
A CO2 tank needs some dosing(NPK, traces), a non CO2 tank grows so slowly that fish waste/food supplies the nutrients for the plants and also some from the substrate(Some use soil, mulm, peat etc with gravel flourite etc-generally non CO2 plant tanks have/can have deeper richer substrates).
The substrate issue of replanting is not as difficult since you are not
replanting nearly as much in a non CO2 tank.
But it requires more trial and error with plants and takes more time to
balance the tank out.
When you add CO2, you no longer can add enough fish waste/food to supply the plant's needs. So you need to change methods, use water changes etc to your advantage.
Try adding 10-25% surface area with floating plants, eg water sprite, etc.
Don't do water changes, just top off the tank for evaporation losses.
Water change after pruning.
Add herbivores like Amano shrimps, SAE's.
These will be more effective per critter as algae will also grow slower in
these tanks.
Add more plants/some fast growing types like moneywort, Egeria najas, water sprite, **** tail etc.
Consider adding another 15w/light or a PC light. On a 20 Extra Tall, this is not that much light. 2-2.5 w/gal would do well.
Also, you might want to add a 1/2" of ground peat and maybe some mulm from another tank to the bottom and cap with 3-4 inches of onyx sand.
Then you'll be up and running with the non CO2 approach.
Some fish loads:
2-3 SAE
10 Amano shrimps.
School of tetras, maybe 10-12 etc. School of cherry barbs etc.
A few Cory cats
Small Ancistrus type pleco
Regards,
Tom Barr"
Blackout
Prune unhealthy or heavily infested leaves, scrape algae and clean the tank. If a lot of plants have to be removed due to severity of the infestation, replace with new. Clean out your filter. Do a 50% water change. Cover the tank with something to block out the light and turn off the lights for 3-5 days. Turn off the CO2 also and drop an airstone in the tank. Now sit on your hands (I did mine on a Thursday and left for a long weekend on Friday- not as nerve-wracking that way).
Uncover the tank. Do another 50% water change.
Post-blackout changes
This is partly specific to my tank, so only applies in principle to any other tank.
Original setup: 20xh tank (24" deep), 1.5wpg NO lighting (2 15w tubes), KH 7, DIY CO2 around 20ppm, Onyx/Flourite/gravel substrate, slow growing plants (Crypts and Anubias)
I decided to chuck the CO2, and this is Tom's response verbatim:
"No, CO2? Now things/method need to change. Do not mix these two methods(CO2 vs non CO2/carbon enriched) together.
You might try using Excel, but you may as well use CO2 then.
A CO2 tank needs some dosing(NPK, traces), a non CO2 tank grows so slowly that fish waste/food supplies the nutrients for the plants and also some from the substrate(Some use soil, mulm, peat etc with gravel flourite etc-generally non CO2 plant tanks have/can have deeper richer substrates).
The substrate issue of replanting is not as difficult since you are not
replanting nearly as much in a non CO2 tank.
But it requires more trial and error with plants and takes more time to
balance the tank out.
When you add CO2, you no longer can add enough fish waste/food to supply the plant's needs. So you need to change methods, use water changes etc to your advantage.
Try adding 10-25% surface area with floating plants, eg water sprite, etc.
Don't do water changes, just top off the tank for evaporation losses.
Water change after pruning.
Add herbivores like Amano shrimps, SAE's.
These will be more effective per critter as algae will also grow slower in
these tanks.
Add more plants/some fast growing types like moneywort, Egeria najas, water sprite, **** tail etc.
Consider adding another 15w/light or a PC light. On a 20 Extra Tall, this is not that much light. 2-2.5 w/gal would do well.
Also, you might want to add a 1/2" of ground peat and maybe some mulm from another tank to the bottom and cap with 3-4 inches of onyx sand.
Then you'll be up and running with the non CO2 approach.
Some fish loads:
2-3 SAE
10 Amano shrimps.
School of tetras, maybe 10-12 etc. School of cherry barbs etc.
A few Cory cats
Small Ancistrus type pleco
Regards,
Tom Barr"