How do I cure my algae problem?
Can you please tell me what has caused the black algae on the plants in my 240 l mbuna tank, and how I can get rid of it? My tank has two filters and I do 50% water changes every week. The set-up has been running for six months and is stocked with 40 juvenile mbuna, four Cuckoo cats and a Bristlenose plec.
The algae is driving me crazy. All my water parameters are fine — please help! MIKE, HULL
ALooking at the pictures you sent in and also from your description, the problem you are having is with black brush or beard algae. It is extremely common on plants like Anubias that have slow-growing, long-lasting leaves. Like all algae, there’s a mix of reasons for its appearance in an aquarium. Bright light together with relatively high nitrate and/or phosphate levels are important factors, but the absence of fast-growing plants that can outcompete it for light and nutrients should also be considered. Water chemistry may be important too, brush algae seeming to prefer water that is hard and alkaline.
Other than Siamese algae eaters and the more strictly herbivorous livebearers such as Ameca splendens, few aquarium fish consume brush algae, so its control is usually about getting the environment right rather than adding something to keep it at bay.
Floating plants are a quick fix, but at the very least you want to make sure that your Anubias are not sitting directly under any bright light. These plants do best in shadier spots where the light is somewhat filtered through green foliage, so you might want to think about adding some other hard water tolerant plants to your system, preferably ones that are tall and fast-growing, so quickly able to provide the sort of shade your Anubias need. Options might include Vallisneria, Sagittaria, Crinum and some of the hardier Echinodorus species.
You also want to check whether your plants are compromised in some way. Lack of proper fertilisation and insufficient carbon dioxide levels can cause plants to grow more slowly than they should, and this makes the appearance of brush algae more likely. Anubias respond well to the use of liquid fertilisers, being epiphytes, while casual aquarists might find adding the fertiliser tablet to gravel around clumps of Vallisneria and other rooted species significantly improves their growth rate. Either way, happier plants means life becomes more difficult for algae, which is exactly what you want here!
Frequent water changes, moderate stocking, fast-growing plants, and the removal of any uneaten food will all be useful ways to ensure nitrate stays nice and low and algae can’t get a foothold.
Beard algae on Anubias.