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Global Moderator
Staff member
15 Aug 2013
Lelystad, Netherlands
General plan of attack in case of algae/bad plant growth

We see this question about 10 times a week and to answer each time gets old in the end. So, I decided to give some general guidelines most experienced people here think are solid suggestions

1) Light

Not mentioning specific lights, the list gets outdated very quick, and all must choose within their budget, but we mostly see to much or to long light. In order to get everything established 6 hours of light will be plenty in the beginning. Also, it’s very easy to give to much light, make sure it’s a dimmable light (usually start with 30-50% especially with the fancier modern lights) or that you can increase the distance to the substrate (intensity decreases squared with distance). Blocking with tinfoil can also be helpful. Only if all is going well SLOWLY increase force and time, let everything adjust and increase again.(

2) CO2

In layman’s terms: light creates metabolites in the plant which can damage the plant tissue if they aren’t caught in time. More light gives more metabolites. Plants can handle these larger amounts, but they need time to adjust to the increased amounts (read multiple weeks). CO2 is one of the ingredients in handling, so more light will increase CO2 demand. It is far easier to increase the light than it is to increase the amount of CO2 available to the plant, thus damaging the plant and causing bad growth and algae. Plants can do perfectly with the amount of CO2 which occurs naturally in water, just adjust the amount of light. If you want to use a lot of light you will NEED a LOT of CO2.

Getting plenty CO2 in the water isn’t easy, see our website for articles and forum messages about that(

3) Ferts

Plants need to eat, especially to grow. The fertilizers (ferts in short) can be divided in 1) macro components : N, P, K/Mg and micro components ( things like Iron ). Since it’s hard to measure those easily ( we don’t like water tests: we advise the EI method in which we add plenty and dilute that with water changes. When using salts this is also the cheapest solution ( If you buy ready made solutions make sure they contain all the needed macro’s and micro’s (not always the case!)(

Relying on fish poop to fertilize your plants can be done, but you will need a keen eye to balance light, amount of plants and amount of fish/feed. If you read this you will have troubles, so I would add ferts.

Oh and repeat after me: ferts don’t cause algae, ferts don’t cause algae, ferts don’t cause algae, ferts don’t cause algae, ferts don’t cause algae, ferts don’t cause algae, ferts don’t cause algae. This has been extensively proven.

4) Water

You can use regular tap water for 98 % of all plants to grow. There is no need to use anything else. The only exception is chloramine/chlorine in the tap water. If this is in your tap water you will always need to prepare it to remove this.

Even if your tap water is very hard (liquid rock) there are plenty members here who have grown beautiful plants and tanks. Especially if there are problems it is far easier to do large and regular water changes with tap water. These will remove pollutants from the tanks and combined with manual algae removal will increase the health of the tank.Only in rare cases softer water will be needed, cutting it with rain water (50/50) is a solid way to lower hardness. Using RO is rarely advisable .(

5) Substrate

Plants really can grow in everything. Some substrates are a bit easier or give more room for mistakes, especially in fertilizing regime, others are a bit harder but far cheaper. Some only use expensive “Gucci” substrates, others only use regular sand. As long as you add the needed amount of ferts, and the substrate doesn’t leak toxic substances, use what you prefer.((


If you succeed to give enough ferts and CO2, the next thing that becomes important is flow, all this has to be brought to all parts of all plants and this is harder than it seems. In general, we will advise to use flow in the tank to about 10 times the tank volume. This stems (see what I did there 8>) from the manufacturers often overstated claims of pump volume delivered. Goal is to see all plants gently moving in the flow. One of the better ways to create this is with a full-length spray bar (

7) Here are some extra tips/tricks

· Start with a lot of plants (can be cheap pond plants), more plants make a more stable environment.

· Floating plants can help with blocking excess light

· When you encounter problems making a journal with all relevant data and pictures will help with problem solving

· There is a huge amount of info on this forum, please invest in some reading time here, most all questions have been asked and answered. Make sure you read the stickies

So, in short: when there are problems:

· Decrease the light to 5-6 hours (no siesta or ramp up/ram down times)

· Use ferts, everything needed

· Do large (50%) and regular (2/week) water changes, combined with improved maintenance

· Do all of the above for at least two weeks to see if things change, if everything improves and start growing healthy, you can gradually start to increase lights and decrease water changes
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