How To Increase Flow

So I’m struggling with B/G algae on the crypts along the front glass of my 20 g long. It’s on the glass along the sand too. I read still water, excess light and too much nutrients are the cause.
1. How can I increase the flow around the bottom of my tank?
2. Should I upgrade my Aqueon 10 HOB to something more powerful?

Current stock:
6 Serpae Tetra
6 Danio
3 Otos
2 Nerites

40% water change weekly.

Plants have BB algae on them and need replaced so they can help with excess nutrients and nitrates.

I’m messing around lowering my light settings, but I really don’t know what I’m doing.

Any help appreciated.

It looks more like black beard algae than blue green algae (bga) on the plants.

Blue green algae (Cyanobacter bacteria) likes red light, low oxygen levels, slow water movement and nutrients.

If you use Fluorescent globes, replace them at least every two years and get globes with a 6500K rating (K is for Kelvin). You should also replace the starters when you replace fluorescent globes.

If you use LED lights, have them set on 6500K (daylight). LEDs don't have to be changed and will continue to provide the same light their entire life.

You can increase water movement with an air pump that is attached to some airline and a plastic multi-coloured airstone. You already have an airstone in the tank. If it's not blowing much air, you either need a bigger air pump or the airstone is blocked up. The multi-coloured plastic airstones can be taken apart and cleaned and put less back pressure on the air pump so you get more air in the water. You can also get a small internal power filter and put it near the bottom to help improve circulation. The airstone will help improve oxygen levels in the water too.

To dilute nutrients, stop adding plant fertiliser for a few weeks and do a 75% water change and gravel clean the substrate every day for a couple of weeks. Try to physically remove as much of the algae as possible. If there is bga on the glass, wipe it off each day with a sponge or paper towel. If the algae is on ornaments, take them outside and hose them off, then put them back in the tank.

Black beard algae is more difficult to deal with and reducing nutrients and having the right coloured light (6500K) helps.

There's no need to replace your live plants unless they are rotting and dying.

If you can't get rid of the bga using the ideas above, you can get something like Ultralife blue green slime remover

According to Aqueon, that filter is good up to 20 gallons. That makes it the bare minimum size, and with the cartridge insert design, it isn't very good. Cartridges were designed for the filter sellers, as previous designs didn't need replacement parts. You bought them, rinsed the media, and it lasted for years with no new purchases. So cartridges came in for a revenue stream, even though they are inferior to older designs.

I would consider adding a second filter,or getting one rated for a larger tank. Other than that, Colin has it covered above.

GaryE said:

According to Aqueon, that filter is good up to 20 gallons. That makes it the bare minimum size, and with the cartridge insert design, it isn't very good. Cartridges were designed for the filter sellers, as previous designs didn't need replacement parts. You bought them, rinsed the media, and it lasted for years with no new purchases. So cartridges came in for a revenue stream, even though they are inferior to older designs.

I would consider adding a second filter,or getting one rated for a larger tank. Other than that, Colin has it covered above.

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I have an Aqueon HOB with a cartidge holder on a 10 gallon. I threw away the carbon cartridge, cut a piece of foam to size and put that in the cartridge holder. I also crammed a mesh bag of bio beads into the filter too.

This is blue/green algae which is actually not algae, it is cyanobacteria.



I agree with Colin that you do not appear to have BGA but rather BBA (Black Beard Algae).

Blue green algae (Cyanobacteria) can come in a range of colours from green, dark blue, brown, black, purple and red. It will lift off in a film/ sheet and smells musty mouldy. It can also irritate your skin and eyes so wash your hands with soapy water after handling it or working in a fish tank.

So, the picture in the op was after my water change yesterday. I had already removed the sheets of bga that form around the bottom and just above the sand line, and under the crypts.
Attached are 2 pics of spots that have already come back.

I think my LEDs are set to 5000k, I only have the choice of 5k and 12k.
My lights have a sunrise/sunset routine programmed in that I tweaked to reduce light output %. I did have a few period a day of 20, 40 and 50% red. I have reset the reds to 0. Pic attached of my new schedule.

I haven’t used the standard HOB filter cartridges with the exception of the past couple weeks to help clear the water of the AlgaeFix I used. (that was another post you all helped me with). I’m back to my regular ceramic media in a bag with a sponge. (see pic). Up for any suggestions if I need to change that up. I will look for a larger filter soon. Need to complete a few out of town trips first.

I changed the air stone out. My old one was pretty blocked.

The only fert I have been using is Flourish Excel with water changes. There were root tabs in January.

This device might help. It sucks water from the top and pushes it down, creating flow at the bottom of the tank, and cleaning up the surface water. Surface Skimmer (Amazon)

I've had BGA on a couple of tanks and one to two treatments of Ultralife Blue Green Slime Stain Remover (Amazon) fixed it on those for me.

Just Add Water said:

The only fert I have been using is Flourish Excel with water changes. There were root tabs in January.

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Excel isn't actually a fertilizer. It's an algicide. It goes by the theory that killing algae frees up nutrients for the plants. Problem with that is plants can already outcompete algae for nutrients.

Just Add Water said:

The only fert I have been using is Flourish Excel with water changes. There were root tabs in January.

Click to expand...

Excel is not a fertiliser so the plants may well be missing nutrients. Try using Seachem Flourish Comprehensive Supplement instead, and new Seachem Flourish root tabs for the root feeders - the root tabs need new ones every 3 to 4 months.


Excel is actually a 'liquid CO2'. They say it's not an algaecide

Because some people have observed reduced algae when using Excel, some people try to use it to treat unwanted algae. We do not produce or market it as an algicide and using it as spot treatment where it is overdosed or applied directly to a plant can cause damage.

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from the FAQs here https://www.seachem.com/flourish-excel.php

Blue green algae can be a seasonal problem, depending on where you are. In my club, we'd all get it in Spring for a few weeks, and then in late summer. Once we realized it was appearing in a lot of different tanks in different houses the same week, all we could do was fight it with the lights out treatment (total darkness, towel over the tank for about a week) or the somewhat expensive red algae products. It's awful stuff, but it follows its own rules. Cyano and I are old enemies, and so far, the battle tends to end in a series of draws or border skirmishes where we engage, then retreat to our own corners to fight again...

Just Add Water said:

I think my LEDs are set to 5000k, I only have the choice of 5k and 12k.

I haven’t used the standard HOB filter cartridges with the exception of the past couple weeks to help clear the water of the AlgaeFix I used. (that was another post you all helped me with). I’m back to my regular ceramic media in a bag with a sponge. (see pic). Up for any suggestions if I need to change that up. I will look for a larger filter soon. Need to complete a few out of town trips first.

Click to expand...

5000K is fine and will do the job. A 6500K would be better but 12000K is way too high and has too much blue so 5000K will do.

You don't need a bigger filter, just stay with what you have. Ceramic beads and sponge is fine for filter media.

The new pictures do show blue green algae so try cleaning up conditions and stop fertiliser for a few weeks. If you still can't control it, use the ultralife blue green slime remover.