jayne said:
...I must admit that I am a bit concerned about the amount of plants I need to buy, I know that the only way to help to combat algae is by planting heavily from the start...
jayne,
Combating algae is much more than about having xyz number of plants. It's better to take a "holistic" view of a tank so that we can see it from an ecological and environmental standpoint. Having lots of plants does not in and of itself prevent algae, but is a significant element in a system, or approach which helps to establish and stabilize the tank's ecology. Too many people look at a tank and see only it's size or only it's plants or only the fish. Few people ever consider the real workhorse of a planted tank which are the bacterial colonies. The same biology at work in a small tank is also at work in a big tank. The trick is to think about how to efficiently accomplish the ecology for the tank.
Your question regarding number of plants was addressed in this thread=>
viewtopic.php?f=3&t=1612&p=16764#p16764" onclick="window.open(this.href);return false; which, for the number of plants you get is a bargain. You can fill in the key spaces by purchasing additional specimen plants and you can decorate the wood by tying ferns and large anubias to it. The only way to avoid the stringy look of stem plants is to prune them frequently which will make their stems thicken and become more robust.
But this is only part of the story. One way in which algae is typically triggered is by high light combined with a high or unstable ammonia loading rate in the water column (there are other trigger mechanisms but these two have the highest correlation). In order to reduce the risk therefore you can start the tank with reduced lighting and limited photoperiod.
Ammonia production is combated primarily by bacteria. During tank startup the bacterial populations are low and unstable. Therefore the filter media you start out with should be media you currently have in use. More importantly, the substrate needs to contain bacteria colonies and should be seeded with organic material such as peat, which provides carbohydrates for the bacteria.
I believe you mentioned that you intended to use a so-called enhanced substrate such as Ecocomplete. The organic material in the sediment will provide food for the bacteria and the high quantity of plants will pump oxygen into the substrate enabling the bacteria colony to grow and to oxidize the ammonia. The goal here therefore is to accelerate the growth of the bacterial colonies.
Plants that develop large root structures are significant in that they do a much better job of interaction with the sediment and experiments have shown that the area of sediment surrounding large rooted plants such as Swords and Crypts are better oxygenated than areas having plants with lesser developed root structures. My feeling therefore is that the planting of these types is advantageous, especially in a configuration such as yours where sediment/root interaction is imperative.
The addition of CO2 enhances the plants ability to produce food for the bacteria and to oxygenate the substrate. Plants will also directly remove some of the ammonia from the water column. The more plants, the greater will be this ammonia removal, the higher will be the oxygenation rate and the faster, more stable will be the rise in bacterial population and diversity.
So the combination of substrate bacteria seeding, filter bacteria seeding, CO2, nutrient dosing, high plant density and lower lighting will all combine to reduce the development of algae.
The remaining item is water changes. Although I can appreciate the size of the tank, neither ammonia nor algal spores are sympathetic to your water volume and they will populate the water column to a significant degree. Serious thought should be given to water changes regardless of tank size. Water changes is the single most effective way of algal spore and ammonia removal so the more it is accomplished the better off you will be. There is also no need to use RO water exclusively as tap water will serve the purpose, so the issue of water changes should be at least considered.
Cheers,