Damn. Cyanobacteria

[malevolentsparkle]

So Ive got cyanobacteria in my tank. I know the usual causes and they don't seem to be the cause, so if anyone can help me that would be great:

I do weekly(ish) water changes (around 15%), don't have high light (just 2x t8s), have a decent current (exp. where the cyanobacteria is), don't overfeed, and have plenty of plants. It seems to grow mostly on my wood.

1. I use proper pH 6.5 which has a phosphate buffer. could this phosphate be feeding the cyanobacteria? or could my tap water be high in phosphates?

2. I recently put a 6500K tube on my tank. This is a reptile tube so it has increased UV. I thought that the glass top would block the UV, is this the case and if not could the UV be helping the cyanobacteria along?

thanks.

[Jennifer]

Phosphates aren't bad for the tank, nor do they cause algae. That is a myth. Imbalances in light and CO2 cause algae as do poorly growing plants. If you don't have plants, then turn off the lights. If you do have lights and plants,then do the following:

Remove all detritus and cyano that you can see and keep doing that every other day

Increase your water changes to 50% once weekly

Add a liquid carbon supplement (normal doses of Excel every 24 hours)

Add a nitrate supplement and potassium supplement every other day for the plants

Add a trace nutrient supplement for the plants

Decrease the lighting intensity or photoperiod by half

Rationale: the supplemented nutrients will get the plants growing well so that they can use the nutrients in the water column and the cyanobacteria won't have anything to feed on. The water changes will prevent buildup of 'leftover' nutrients that can cause imbalance and it will also attack the cyanobacteria with a burst of CO2 dissolved in the fresh water. The liquid carbon is a 'nutrient' that will help the plants grow - if you don't already have CO2 injection. Too much light will cause algae so cut it back, but not completely off at this stage since we want the plants to start growing faster. If the problem persists, you can do a blackout of the tank.

[Brennos]

I did what Jennifer said, and it has pretty much cleared up. I still had a bit between plants and the glass (no flow), so I removed some of the sag from the front of the tank, and left a 2cm buffer zone, so far so good.

[malevolentsparkle]

thanks that sounds doable. just need to get a carbon, nitrate and potassium supplement. got the trace.

[malevolentsparkle]

so thinking Seachem Flourish Excel, and Nutrafin Plant Gro NPK will that be ok? I already have a bottle of Seachem Flourish. buying the seachem macro nutrients separably gets pretty expensive.

[Jennifer]

Yep, those three should be sweet. Keep in mind, it will take the plants at least a week to start kicking into gear so it won't happen instantly, but it will happen.

[malevolentsparkle]

all right, despite me having little money and time at the moment (new baby) I've managed to beat it it seems. my beard algae is gone too. just reduced photoperiod, big WC, added nitrogen, carbon, and micro-nutrients. Did a big clean up too, there was a lot of dead leaves from my stargrass (still not growing right, but time will tell).

thanks for your help!

[Jennifer]

Well done. You must be doing something right. Hopefully your plants will be starting to look good too.