I've got a bit of a problem in my saltwater setup, and I need some help to determine why this is happening. Firstly I'll explain my problem, then I'll go into detail about my setup.
My setup is approx 7 months old. When I first setup I cycled for 6 weeks allowing the bio. filter to establish itself. I slowly added live rock, then over the last 7 months I've added both fish and coral. About 2 months ago my first casualty was my mandarine fish, then all was good for a while. After that my Helio Fungia Coral started to die off, it's now completely dead, and skeleton removed from the tank. In the last 2 months I've now lost a puffer fish, a purple urchant, a dottyback, an anemone, and a small feather coral.
My setup is as follows;
Still in my tank I have 2 orange and white clowns, a sand gobby, 1 anemone, a hard coral I believe is a form of trumpet coral, a large algie eating snail, and another hard coral I believe is a form of frogspawn coral.
My tank is a 90 litre (approx 24 gallon)
approx 3-4 kilo (7-8 lbs) of live rock
2 inches of crushed shell grit as base
Canister Filter, 440 litres per hr (97 imp. gal/h)
(I have an algie eliminator sache in the canister to keep algie blooms to a minimum)
Small protein skimmer
Tank is kept at a constant temp of 25 deg. c (approx 70-73 deg. f)
Amonia level is constantly 0 ppm
pH level is constantly 8.0 to 8.2
Nitrite level is constantly 0ppm
Nitrate level fluctuates between 20 to 40 ppm
Salinity level is constantly between 1.020 and 1.030
Twin globe marine light, turned on for approx 8 hrs per day (I dont actually know the make, but it was supplied with the tank and is fitted to the top of the tank by mounts on each side as my tank is open lid)
Natural light can reach the tank, but only a small portion of light as the tank is on the opposite side of the room to the lounge window, and the light only shines in as the sun is setting
I test every weekend, using an API Master Saltwater Test Kit
My fish are fed daily on New Life Spectrum Marine Formula, and every couple of weekends I also feed them live brine shrimp
My anemones (only one now) are fed white bait, approx once a fortnight, thawed from the freezer
I was generally doing a 25% water change every second week, but since things started dying I've been doing a 5-10% water change almost every night for a week or so.
I hope I've given you all enough info, and I hope someone can tell me if I'm doing anything wrong, or what my tank issue is and what I can do to stop everything from dying off.