My plan to fight cyano

[Nicole]

I have a 72 gallon bowfront with a fairly heavy fish load: 9 rainbows, 5 clowns, 3 yo yo loaches, 2 shistura, 1 bristlenose pleco, 2 otos. It has a Fluval 404, Flourite substrate, 2 8-month-old 54 Watt T5HO bulbs and one diy CO2 reactor. Phosphate is 0.6: too high. Nitrate is 0: too low. Nitrite and ammonia are also both 0.

The tank was running well for a year before I added live plants. Have been trying to learn as much as I can and establish a balance ever since I started with it. I think I've gotten close to a balance a few times since things looked good, plants were healthy and growing and algae was at a minimum. But I've been battling one kind of algae or another off and on for the duration of the live plant setup. Most of the stem plants that I started with to outcompete the algae have flourished in great abundance and then died back. The wendtii is doing well, but with the loss of many of the stem plants the anubius and java fern are getting too much light and are covered in algae.

And now I am battling cyanobacteria. I have been doing lots of reading and feel prepared to fight it. I have put together a plan of action, but I'm unsure of a few steps. Specifically, when to add new plants to help out-compete the algae once I get things in balance and when to start dosing with nitrate (which I've identified as a major contributor to my problem) Any comments on my plan would be greatly appreciated.

1. remove as much as possible manually
2. do 50% water change
3. treat with EM at 1/2 dose for two days
4. do 25% water change
5. treat with EM at 1/2 dose for 2 more days, or possibly longer if cyano is not gone
6. do 25% water change and clean filter well to remove any rotting cyano
7. add new T5HO bulbs
8. NOW WHAT? Do I add nitrate and plants simultaneously? How do I keep the cyano gone once it's gone? Should I get a phosphate absorber for the filter?

I know that I need to get phosphates down and nitrates up. I have added a powerhead to increase water movement and I've cut back to feeding every other day. But I really wasn't overfeeding before!

Thanks in advance for your help.

[SCMurphy]

Use your plants as the phosphate absorber, stimulate their growth and they will take up the available phosphate. This means that when you are done with your eradication treatments you will need to continue to support the growth of your plants by fertilizing them. You will have to add micro and macro nutrients and probably more CO2, I don’t think you can consistently get enough CO2 from a DIY set up for a 72 gallon tank. Just don’t over do the iron or you will replace the cyanobacteria with black brush algae. When I say micro and macro nutrients I mean you will most likely need to add potasium and CO2, and lesser amounts of iron, magnesium, and calcium.

Whenever I perturb the balance of a tank it always runs through 2 or 3 algal infestations before it settles back into balance in a couple weeks. The key is to be consistent (and patient) in supplying the plants what they need to take up the nutrient that the algal bloom is thriving on. That way as the bloom dies back the plants take up the nutrients the algae die off releases so that the algae can’t take it back up and bloom again.

[Daemonfly]

NitrAtes seem to be the limiting factor instead of the more desired low phosphates. Try dosing some extra Nitrate (KNO3 (potassium nitrate)) to get to more acceptable levels (5-10ppm). The plants should then use up the phosphate & out-compete the cyano. Also, cyano is usually found in planted tanks with low(zero) nitrates being the limiting factor.