In planted environment, freshwater aquarium plants need nutrients like ammonium (NH4), nitrate (NO3) and phosphate (PO4) to thrive. But if the fish tank plants consume the excess nutrients, why algae bloom still happened? You should consider following factors :
Aquarium Location. Exposed aquarium towards direct sunlight will promote algae growh. It's true that freshwater aquarium plants need enough lights to thrive, but sunlight contains red-spectrum light that only need by algae. That's why we should put the aquarium at the location where can't be reached by direct sunlight at any hours, only a few hours of sunshine is enough for algae bloom!. You can use a sunshade to reflect the sunlight if you can't move your aquarium to other location.
CO2 level vs Aquarium algae.
Some observations by aquarists concluded that CO2 concentrations in planted aquariums have a major impact to aquarium algae !. Excess Nitrate (NO3) and Phosphate (PO4) only have a little impact for stimulating growth of aquarium algae. Poor CO2 stimulates algae growth!. You should keep the CO2 concentration at a recommended level for aquascape, not only for photosynthesis purpose but also to keep down the algae growth.
What if keeping the CO2 level has contradictory implication with other effort to create healthy planted aquarium ?
Water's surface agitation, splashing water and aeration -which are important for gas exchange and put oxygen into the tank- are strictly prohibited by some aquarists. In their opinion, all of them can throw away the precious CO2, while oxygen will be provided sufficiently by the fish tank plants as a result of photosynthesis during the day. But what about the effort to prevent water's surface problems like oil slick or surface scum? Water's surface movement is important to stir up the surface's water and prevent the classical problems. From my experience, there are some ways to settle this contradiction :
Use Surface Extractor or Surface Overflow Box. They will take out /extract water from the surface to be filtered by existing filtration system (s.a canister or wet/dry filters).
Unfortunately, only small proportion of ammonium (NH4) and phosphate (PO4) can be utilised as a nutrient by freshwater aquarium plants. Phosphate pollutions come from fish food, using non-phosphate-free aquarium fertilizers or your tap water. Algae in aquarium can store phospate in considerable amounts and therefore can live for a very long time with lack of phospate condition. Partial water changes at regular basis (weekly/bi-weekly) and substrate-surface vacuuming can reduce the excess nutrients. It's also depend on how much & how frequent you dose the plants nutrients. You can read more about how to dose plant nutrients in our Aquascape articles.
You should also check your water parametersregularly. Ammonia (NH3) and Nitrite (NO2) levels should be zero. Nitrate (NO3) level below 40 ppm and Phosphate (PO4) level below 1 ppm.
Plant care. Don't let your completely-submersed fish tank plants overgrow and fill-up the water's surface (it's different from freshwater aquarium plants that can grow emerged with their tops in the air), it will limit the gas exchange and creates many water's surface problem such asoil slick or surface scum. Overgrown plants will also reduce middle-water circulation creating anaerobic zones. Prune the fish tank plants regularly, it will encourage new growth and make your freshwater aquarium plants bushier.
Stocking & Feeding. Besides recommendation for population measurement that mentioned in Fish-only tank, you should pay attention on choosing fish species for your aquascape purpose. I recommend to keep small size & ungreedy fishes like tetras or small barbs, they are very beautiful for aquascape but produce less waste. Also do not overfeed your fish to avoid over nutrition.
Lighting. Choose the aquarium lights carefully !, you should read our complete article for better understanding. Switch the aquarium light on for 8-10 hours (max. 12 hours) continuously for successful freshwater aquarium plants' photosynthesis, use a timer to ensure a regular cycle everyday.
It's important to remember that :
Insufficient intensity of aquarium light can't create good photosynthesis and can't be compensated with longer lighting time.
Fish tank plants only need 8-10 hours of good lighting for photosynthesis, beyond that the plants will 'sleep' and the light will only be used by aquarium algae.
Temperature. At the higher temperatures, O2 levels decrease especially during the summer. Use an aquarium chiller to keep the temperatures stable. Higher temperatures make the bacterial metabolism accelerates and uses up lots of oxygen for nutrient recycling. In planted aquarium, keeping good oxygen levels is as important as keeping good CO2 levels.
Filtration. Clean your filters regularly. Keeping bacteria population is important for successful aquarium cycle process, partly clean your biological filter media by turns -using filter bags and rinse it in it's own aquarium water. Wet/dry filteris the best biological filter. Add Hang on Back (HOB) filter for secondary filter (mechanical filter).
Algae eaters. Certain fish, crustaceans and snails can also help a lot in maintaining hygiene in a planted aquarium and combating certain types of aquarium algae.
It's already stated previously that CO2 concentrations in planted aquariums have a major impact to aquarium algae. In non-planted environment, we can't just add CO2 to the tank for the purpose, it will kill your organisms. So, we can only concentrate on other possible inducement factors like ammonium (NH4), nitrates (NO3) and phosphates (PO4). Because no freshwater aquarium plants will absorb the excess nutrients, it will be absorbed by algae in aquarium, creating algae bloom. Handling aquarium algae in non-planted aquarium is simply to reduce those parameters.
There are some preventive actions to keep down aquarium algae growth :
Aquarium Location. Don't let your aquarium exposed to the direct sunlight, even only for a few hours. It will provide energy for aquarium algae to create algae bloom. If you can't move your aquarium to shaded area, use a car sunshield to keep out the sunlight during the shining-time.
Partial water changes at regular basis (weekly/bi-weekly) and substrate vacuuming are very important to reduce excess nutrients.
Stocking & Feeding. You should limit your fish population in your aquarium. Recommended measurement of fish-density: 3 litres of water for 1 cm of fish length. If your aquarium water volume is 300 litres and average length of your fish is 5 cm, population recommendation = 300/3/5 = 20 fishes only. Also do not overfeed your fish to avoid over nutrition. [NOTE : 1 US gallon = 3.785 liter ; 1 inch = 2.54 cm]
Water circulation. Good water flows are important, not only for spreading out oxygen and leveling temperature, but also make aquarium algae difficult to stick to any surface.
Water's surface agitation. This is very important for gas exchange - releasing waste gas and taking oxygen into your tank. Good surface agitation can make your aquarium water smell fresh.
Filtration. It's very important to provide plenty of surface area for bacteria habitat within your aquarium and filter. Bio Substrate andSponge filters are highly recommended for Biological media within your aquarium, while Bio Filter Media s.a : Bio Filter Substrates, Bio Balls or Bio Rings are inside your biological filter.
Excess organic matter shouldn't be suspended /free-float, it should be caught in the filter or Biological Substrate where they belong. It is these fine suspended particles that continue to pass through the filter that cause the Green water.
Clean your filters regularly. It
would be better if you use filter bags and partly clean your biological
filter media to keep enough bacteria population.
If necessary, add Beneficial Bacteria directly into the water or spread directly on to your filter pad or media to immediately establish biological activity to stabilize aquarium environments.
Denitrator. There are many methods of nitrate reduction, one of them is Denitrator (Nitrate Removal Filter). It is also known as a denitrifier, biodenitrator, anaerobic biological filter, or simply a nitrate filter.
Denitrator is relatively a new device. So far, there are 2 methods available in the market :
1.Sulfur Denitrification. This method has been used for years in commercial water treatment. It uses Sulfur media to harbor a specific species of anaerobic bacteria for denitrification process and combines with Carbonate reactor (Calcareous media) to neutralize the acid (pH buffering).
2.Comprehensive Biological Filter. It contains at least dozens of different species of BOTH aerobic and anaerobic bacteria and will completely break down all organic matter that passes through it into gasses that escape into the atmosphere.
This method has capability of reducing organic solids and Ammonia (as a common Biological filter) and as well as just Nitrates (Denitrator).
Phosphate Removers. Basically, there are 2 types of products in the market :
1.Phosphate Remover Media is a Chemical Filter media that usually contains ferric oxide, an iron-based phosphate binder ideal for use in aquarium filters, it will absorbs phosphate, silicate, and organic compounds without leaching adsorbed substances.
2.Liquid Phosphate Remover usually contains Lanthanum as the basic ingredient. Lanthanum has an affinity for phosphate molecules, basically binding with and forming Lanthanum Phosphate, it also has (although not as high) an affinity for Carbonates which in the absence of phosphate it will bind out of the water.
Therefore, you should check with a testkit whether there is any phosphate present and secondly add a little KH Buffer
before and after dosing so as to maintain your current KH levels.
The cloudy seen after dosing depends on the concentration of phosphates ie. slight haziness- low phos levels, milky appearance-high phos levels.
Lanthanum phosphate / Carbonate is easily removed by skimming or other forms of mechanical filtration like filter wool etc.
Lighting. You shouldn't switch the aquarium light on for hours. Switch the light off after you finish enjoying your aquarium, too much light in plain-tank will only be used by aquarium algae for photosynthesis.
Algae eater fish. Algae eater fish will help a lot in combating certain types of algae in aquarium. You should carefully select it, some algae eaters prefer fish food than algae - they only add more waste to your tank!.
Aquarium Algae 
before and after dosing so as to maintain your current KH levels.
