Fertilising a planted aquarium while eliminating algae

The Estimative Index (EI) was developed by Tom Barr and others. It is a method of ensuring that aquarium plants receive sufficient levels of nutrition without recourse to expensive testing kits and the like and with no danger of overdosing and harming the fish population.

Plants require certain nutrients and other elements in order to survive (See “Aquarium Plant Nutrition”)
Some of these nutrients might be provided by the fish population but some, if not all, will have to be added to the tank There are many proprietary fertilisers available which are specifically designed for use in an aquarium including products made by companies like Easy Life and SeaChem.
The big question however is “How much do my plants require?” The manufacturers do give recommended doses of course but the amount of nutrient required will depend on a number of factors including:-
Plant density, light intensity, growing conditions, and the availability of CO2 etc. Manufacturers will also ere on the side of caution and so plants may be lacking in certain nutrients. On the other hand excess fish food could be allowing phosphate levels to build up or nitrate levels could be rising from fish excrement.

Given these problems many aquarists resort to buying test kits which can be expensive and unless you spend a great deal of money are often unreliable.

The EI system is designed to ensure that plants receive an adequate supply of all the nutrients they require in order to thrive – without allowing an excessive build up of chemicals which could become harmful to both plants and fish.

It is based on two principles:-

1. Dosing quite large amounts of nutrient at regular intervals.
2. Regular and relatively large water changes.

The “Estimative” part of the EI system refers to the amount of nutrient required. The estimate is based on the maximum amount of nutrient that plants might need assuming that they are growing under ideal conditions – with maximum light and CO2 levels etc. In practise these ideal conditions will not occur and so the plants will have more than a sufficient quantity of nutrients.
This may sound alarming and you might assume that there will be a gradual build up to excessively high levels. In fact, as long as frequent and large water changes are carried out, the concentration of nutrients will level off. (See article on water changes)
Another cause for concern might be the potential cost of adding large amounts of nutrient only to discard some of the nutrients with the water change, but if the nutrients are added in the form of ‘dry salts’ which are very cheap when compared with the cost of some commercial fertilisers, then the EI dosing system is not at all expensive.
In fact the amount of dry salts required are quite tiny and it is often better to mix the salts with water to produce ‘stock solutions’

If you don’t want the bother of mixing up stock solutions that’s fine, Easy Life, for example, do produce all of the necessary nutrients – Nitrogen, Phosphorous, Potassium, Iron, Trace Elements and Carbon in their range of liquid concentrates

A major benefit of the EI system is that:-
When plants receive enough light, CO2 and nutrients,
not only will the plants thrive algae will not occur.

Water Changes

Regular water changes are important for the well being of any aquarium. Water changes remove dead and decaying matter from the tank and generally keep the level of what might be described as toxins to a minimum. Without any water changes the levels of these toxins would increase at a steady rate (until fish and plants start to die.) A 50% water change will reduce toxin levels by 50% and if these changes are done regularly (weekly) the amount that has built up over the previous week will be removed.
This will also apply to excess nutrients and although the EI system is based on dosing high levels of nutrients a 50% weekly water change will prevent any build up.

Dosing

It is impossible to say exactly what the nutritional requirements are but the following list is fairly typical of the maximum uptake of a well planted and well lit tank :-

Nitrogen (N) 4.5 ppm
Phosphorous (P) 1 ppm
Potassium (K) 30 ppm
Magnesium (Mg) 10 ppm
Iron (Fe) 0.5 ppm
Carbon dioxide (CO2) 30 ppm
Also required are trace elements.

Note these are weekly levels and would be added in smaller quantities say 3 or 4 times per week.

These nutrients can be found in a number of chemical salts, in particular:-
Potassium nitrate (KNO3)
Mono potassium phosphate (KH2PO4)
Potassium sulphate (K2SO4)
Magnesium sulphate (MgSO4)
Fluidsensor trace mix (Includes iron and other essential trace elements)
The other important requirement is CO2. This can be added as a gas but will require an expensive set up – regulator, needle valve, solenoid valve as well as a gas cylinder. A more convenient method is to use a product such as EasyCarbo which is manufactured by Easy Life and available from Fluisensoronline.

Typical Dose Routine:-
Potassium nitrate KNO3 0.011 gm / litre
Monopotassium phosphate KH2PO4 0.0015 gm / litre
Potassium sulphate K2SO4 0.011 gm /litre
Magnesium sulphate MgSO4 0.035 gm / litre
These should be added 3 times per week, every other day.
On the alternate days add Fluidsensor Trace Mix at the rate of 0.002 gm / litre
Every day add 0.02 – 0.04 ml / litre EasyCarbo

Sunday – 50% water change, add salts (or stock solutions) + EasyCarbo
Monday – Add trace mix + EasyCarbo
Tuesday – Add salts + EasyCarbo
Wednesday – Add trace + EasyCarbo
Thursday – Add salts + EasyCarbo
Friday – Add trace + EasyCarbo
Saturday – EasyCarbo

An important part of the EI system is that the amounts and dose routine are not cast in stone! If you miss a day or are away for the weekend it isn’t going to make any difference. Your plants will survive and your tank will come to no harm.

Stock Solutions

As the quantities of salts and trace mix are very small it is recommended that small amounts of the salts are mixed with water (preferably de-ionized or RO)

References:-
The Barr report
James Planted Tank
UKAPS.org

Comments are closed.