I'll do a big water change on Sunday, cleaning the gravel is good fun only done it a couple of times, if there are to many nutrients would you advise not to use plant fertiliser for a couple of weeks?
I do water changes weekly, should cleaning the gravel be done weekly to?
Interesting with the light, i have different settings so i could always dim it a little to.
There are a couple things to keep in mind here. First, on the light.
Intensity, spectrum and duration are all involved. Duration obviously can be controlled, but it is not a substitute for intensity, or vice versa. The light must be of sufficient intensity to drive photosynthesis, and this varies some according to the plant species; fast growing plants need brighter (more intense) light, slow growing less. This is why some plants, say Anubias, Java Fern, Java Moss, and crypts can do well under less intense light, whereas most stem plants for example will usually not survive because of the low intensity. Spectrum is also a factor; white light is composed of colour wavelengths--look at a rainbow, or light shone through a spectrum--and red and blue are essential for photosynthesis, and green improves the plant's response. If the intensiity and spectrum are OK for what you need, then duration can tweak the light if algae becomes an issue. However, this is not the end of the story.
Nutrients the plants require are 17 in number, some macro and some micro. These must be available to the plants or they cannot use the light. Nutrients can occur from the feeding of the fish and water changes, and in some cases such as low-light slow-growing plants these can be sufficient. The more high-light/fast-growing plants there are, the less likely they will have sufficient nutrients solely from the afore-mentioned, and then you need a supplement. It is safer to use a comprehensive supplement as this provides all necessary nutrients (those left out or minimal are assumed to be provided naturally).
Problem algae can occur when the light is too intense, or too weak, or on for too long, or not on long enough. Assuming the spectrum is OK--if not, you are basically doomed regardless. Problem algae can also take advantage if nutrients are greater than what the plants utilize, or not adequate. This is another reason to use a comprehensive supplement, it ensure everything is being provided. As Colin noted, water changes are good to ensure the balance is reset, but not everything is resolved by a W/C.
Once the balance of light/nutrients is established, we also need to keep in mind that it can be affected by things like the longer and brighter daylight entering the room in summer, or the tank lighting losing its strength (more of an issue with fluorescent tube light than LED).
With the above in mind, I would suggest you go after the light and not eliminate nutrients. This does not mean you ignore the build-up of organics...in the substrate, and in the filter. Keeping these down with weekly water changes including a cleaning of the filter media and substrate in open areas is usually worth it. The fertilizer, if it is a comprehensive one, will be of more importance per say than reducing this and allowing organics to accumulate. For one thing, organics means nitrates likely increasing, and this is detrimental to fish and of no benefit whatsoever to plants in this type of setup (natural or low-tech planted tank).
