Hi guys, Here is my problem, I hope you or someone you know may be able to help. The problem is despite getting what I think is everything right as per the reccomendations and the plants grow healthily (heavily planted with hair grass and riccia at the front, tiger lillies and large leaf plants at the back with mosses on bogwood in the centre) I don't see massive amounts of photosynthesis. I have a very low fish level, 6 x Otticinclus, 4 x flying fox, 6x rainbow tetras. My tank is a trigon 190 filtered by an Eheim Professional 2 external canister filter. The return water is spread via 2 spray bars at 90 degrees keeping a good flow of water moving throughout the tank without too much turbulence. Temperature around 26 degrees. My CO2 system runs off a 2Kg bottle with a PH sensitive electrode. When the PH goes up and reaches 6.8 the CO2 switches on and stays on until the PH reaches 6.5 and then switches off. It usually takes anywhere between 10 minutes and 30 minutes for it to switch off depending on the time of day and how many lights are on. This runs 24/7. The bottle lasts around 4 months. The CO2 goes through the bubble counter at the rate of 1 per second. I can increase the number of bubbles but this just drops the ph quicker and does not necessarily put more CO2 in. I have a permanent CO2 colour indicator inside the tank which shows a lime green to yellow colour indicating that the CO2 is at the right levels. The diffuser is the JBL Spiral type where the bubbles slowly spiral around mixing with water on their way up. I used to use a water driven diffuser from DUPLA but that needed a water supply off the main outlet pipe and looked a bit messy. The JBL one has a gas escape tube at the top and I noticed that CO2 would escape through that and straight to the surface when it built up at the top of the diffuser. I though that this was a waste of CO2 so I have connected a small length of tubing to it and ran it to one of the spray bars where I thought it would get sucked along and pumped through the tank. Instead a small column of water from the spray bar goes back into the diffuser and no more gas is escaping so I gues that this is an improvement. I don't do 50% water changes every week. I use RO water and change 30 litres once a fortnight. I add 20 mls of liquid KH buffer, 10 mls of liquid iron and a flat teaspoon of Sera Mineral salts at each water change. The lights all have reflectors and are all on timers coming on gradually until they are all on around mid day. There are two 24 inch 30 watt Sera tubes in the centre, a smaller 20 watt tube at the back and a 30 watt T5 tube at the front. At the peak all lights are on for around 2 hours at midday and then go off towards the evening. The smallest light comes on at 7:30 am and goes off at 8pm at night. The KH is 4, GH 10. If the PH does not go up the CO2 does not come on. I add KH buffer, the PH goes up and the CO2 comes on. It all seems to work well and I don't have any problem with ammonia or algae, I just don't see the photosynthesis I expect and wondered why. What do think is the problem? Any help appreciated. Thanks, Steve.