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Aquarium Nut
23 Posts
Discussion Starter · #1 ·
My 30 gallon Discus planted tank has a large Algae problem. I've done some research on it & discovered it to be BGA - Dreaded Blue Green Algae. I'm thinking of killing it off with Maracyn. But I'm conserned about also killing off my Bio Filter. Anyone ever used Maracyn to get rid of this plague?
Thanks for any & all help.

1,323 Posts
I posted a reply to another thread on this topic. Did you post it more than one time?

Anyway my first question is what is your phosphate level in that tank? Phosphate can have a lot to do with the formation of that particular plague. You may need something to get rid of the phosphate if it is off the chart first like a phosphate removal pad to float in the water and then the Maracyn can be used. I have not personally used it for that but I have used it in very high concentrations for a stubborn fish infection at the manufacturer's recommendations due to extremely hard water and it did not hurt my biological filter at all. I did remove all carbon from my tank so I did keep close check on my phosphate levels during the treatment as it was used for 15 days instead of the regular 5 with 50% water changes every 5 days to assist the fish.

I do not see a problem but I would be checking for the phosphates first as if this is the problem, you will need to be getting them under control or the algae will be right back.


8 Posts
Hey Tom, what's up with the P-car?

You can try a few things, but the generally accepted method is as follows, first address root cause:

Ensure the plants outgrow/ starve the BGA by ensuring your CO2 is at 15-30ppm, and that the lighting is NMT 8-10 hrs/ day, A 1 hour midday break of no lighting can help.

Make sure the NPK levels are appropriate to fuel the plants. If one is low, then the plants are stunted but the BGA is nourished.

Next make sure the plant biomass is exceeds the nourishment and lighting. Again, this starves the algae.

To answer your question, maracyn can help, and is thought to hit the biofilter as well, but the BGA will come back if you don't address above. Not sure where to get it , but folks at this forum , report that E-mayacin works better on BGA. Maracyn will work at half dose to kick back BGA. Another tip is to slope gravel to front of trim since that is ofthen where it starts. Use a blcak tape line and blackout the gravel. The ambient light in the room is enough to keep that BGA on the gravel/glass interface going. Use paint scraper weekly there as well.

Then if you are clear that the conditions are on target, you will benefit from the following black out procedure decribed by Tom Barr:

Prune snip, clean, fluff, preen, and then clean filters, tubes etc.
Then do a water change, 50% or so..........
Add KNO3/PO4/GH(no traces)
Then turn off CO2, light.
Add a bit more current to the surface.

Cover tank with 2 layers of trash bags etc.

Wait 3 days

Remove bags, turn light/CO2 back on.
Do another 50% water change.

You can add some Excel as well after the water changes.

You can also and likely should do 2-3x a week 50% Water changes followed by Excel, revamp and look at the CO2 much more and watch plants for new growth.

Keep up on things from then on. after a 1-3 weeks of hard work, you likely can back off and relax.

Tom Barr

Aquarium Plants and the Barr Report - Aquatic Plants

maracyn is effective post treatment by cutting up tablets and planting them at the glass/gravel interface to prevent the start of the outbreak and to point kill without dosing whole tank.
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