I've just won a fluval co2 88g system on ebay for a bargain (i think!) and was wondering if anyone could give any advice when using co2 please? I've read a little bit and it says a solenoid is a good idea to tun it off at night and also a drop checker. I can't fit a drop checker due to the lid on my tank, can i get something else?

I presume you mean the drop checkers that hook over the side of the tank? There are other types that will stick to the inside of the tank on suckers that should fit your tank. It is best to have one as you should aim for between 15 and 30ppm of CO2 in your tank, with most opting for 30. Too little and you plants might not benefit and you'll wasting CO2 for no gain. Too much and it could be detrimental to any fish you have.

It is possible to work out CO2 levels by checking your pH and carbonate hardness KH levels and cross referencing them on a table. However unless you doing this several times a day you run the risk of missing a fluctuation that could cause problems. Drop checkers provide that easy instant visual reference at a glance.

A solenoid is a good idea as it allows you to turn off CO2 at night when the plants don't need it. This will save you CO2 and money in the long run. If you do use one connect it to a timer and aim to turn the CO2 on about 1-2 hours before the lights. This allows CO2 to reach optimal levels as the lights come on and the plants start synthesising. Additionally turn it off about an hour before lights out to allow levels to drop back down.

I currently use seachem flourish excel, can I still use it in conjunction with the co2 or should I stop?

There's no issue with using Excel in combination with CO2 if you want to. It's perfectly safe to do so though if you get your CO2 system running well you may not need the Excel.

I've set up my CO2 system now and just want to check the set up with someone please. I've put my diffuser as low as possible and it's positioned below the spray bar from my filter. The drop checker is right up the other end of the tank. I figured I'd get the best overall reading from the tank if it was that way. Does this sound right please?

The diffuser needs to be placed so that the CO2 is best distributed around you tank so it sounds like you've placed it correctly. The drop checker needs to be placed in such a position to indicate CO2 levels are correct throughout the entire tank. As you've positioned is probably best.

Just a quicky, but what is the reading for degrees of carbonate hardness (dKH) of the water you have used inside the drop checker?

It should ideally read at least 4 or you can get false readings when adding the tester solution. I only dabbled with CO2 a few years ago but my drop checker never changed colour to start with despite CO2. It turned out my water was too soft. I bought a bottle of 4dKH water from a specialist plant/CO2 site to get round this problem.

To be honest, I haven't checked it. It was a kit from fluval so I presumed the solution they provide was the normal 4dKH.

I am in the process of setting up a planted tank, complete with CO2. Once that is set-up, I will be adding some tetras etc, lots of small fish. Will the carbon in the filtration system be OK or should it be removed?? Thanks Bill W

My CO2 has been up and running now for a week or so. I've not got money for a solenoid so I'm having to turn it on and off manually.
My photoperiod is currently six and a half hours with a one hour break in the middle. What I'd like to know is, now that I'm running CO2, should I scrap the one hour siesta as I don't turn the CO2 off during this time?
I'm really keen to hear what other FK members do.
Thanks