Is the water still 26C and is there still no airstone/bubble wall? The Venturi in the filter is not the same, an airstone drags the de-oxygenated air from the bottom of the tank to the top allowing for more even gas exchange. The venturi just puts bubbles in the water and that doesn't really make much difference. At the higher temperature the water cannot hold as much oxygen and adding medication exacerbates this. Lack of oxygen can easily cause health problems.
It's been my experience that drop checkers only work if you use a 4dKH solution. In many areas the tap or tank water is suitable but in others you get a continued false reading.
Essentially it's a PH test not really a CO2 test - the theory being that the CO2 creates carbonic acid.
To see what's really going on take a clean glass and fill it from the tank then place it in a well ventilated room for 24 hours. The next day test the PH in the tank and in the glass of tank water you took the day before. If possible check first thing in the morning, at mid day and at night.
You should see the tank's PH change but the glass water PH remains stable. More importantly you will see the differences between the PH of the water that is in the tank and water that has no CO2 added. If this is greater than 1 or if the ph in the glass of water varies then there is a problem - let us know what you find.
My bubble counter started leaking again and I lost the best part of half a bottle of CO2 last week. This gave me the perfect excuse to justify some new toys as a 'cost cutting excersize'. The first was a glass TMC AquaGro bubble counter. Just what you'd expect - no chance of leaks and its a small clear bubble counter with a couple of suckers for mounting to the side or back of the aquarium. The second more interesting item was the TMC Aquagrow Power Diffuser 1500 This is a CO2 reactor for use in large tanks that resembles a bong. The CO2 is piped in at the top alongside a fast flow of water. The water flow spins a prop that churns the co2 and water together the outlet is via a tube with it's opening at the bottom of the bong and exit again at the top. this means the CO2 has to go down through the churning water before it makes it out into the tank. This ensures that only dissolved CO2 or micro bubbles escape thus limiting the waste of your CO2. I bought the 1500 for my 220L tank as I wanted to attach it outside of the tank to the Rena XP3. Unfortunately this was not to be. Despite the supposed design for 1500L tanks and 1000lph max throughput the inlet connector is has an external diameter of a mere 12mm approx. It is glass smooth and no raised lip for secure connection. If I connected this outside the tank I'd be terrified the pipe would one day slip off and the entire tank drained onto the living room floor. Even inside the tank the diameter of the inlet was too small to successfully connect it to my filters outlet pipe. Fortunately I had an old 800lph internal filter of unknown brand sitting in the cupboard and by removing it's outlet guide I was able to jam the two devices together. After that it only took a few moments to complete the setup. I was disappointed that the suckers only fit on one side of the bong and the inlet is not adjustable. This left me with rather an unsightly block of equipment to the right of the tank. I hope and expect that some plant growth will sort this out soon enough. The good news is that it appears to work, and silently at that.
Berlin filtration method requires a skimmer, strong flow, strong light, live rock and a sump or filter for mechanical filtration (only mechanical and chemical). Many people take this a step further and have algae in the sump for nutrient export.
As you don't have a sump you should use the filter but rinse or replace the media often in pure RO or tap water to kill off any nitrosomas. If the filter matures in a standard way it will start to starve the live rock which could result in a reduction of its effectiveness and an increase in nitrates.
Quality live rock deals with waste, ammonia, nitrite and nitrate from a series of organisms that inhabit it from small crustacean down to anaerobic bacteria. The strong light encourages photosynthesis which is important to some of the live rock inhabitants and aids in the process. The skimmer removes organic proteins before they break down into ammonia, with the berlin method it's essential you don't skimp on the skimmer. The sump allows surface skimming to remove the oil film as well as mechanical and chemical filtration, a place to hide equipment and keep macro algae. It also acts to keep the display tanks water level constant. A filter will only do part of this but it can work. I'd keep it as somewhere to run rowaphos and/or carbon when the need arises.
Coral sand can be rinsed in RO water, not tap.
The guy in the shop... 1/ get zero TDS RO, fill tank 50-75%, run for 24 hours to ensure that equipment works and tank doesn't leak. 2/ drain tank again and add egg-crate and coral sand, refill tank - if the RO is still zero TDS it can be re-used. 3/ Add measured quantity of salt to bring to correct salinity slowly. Ensure it all disolves and use a refractometer to check. Leave another 48 hours minimum and recheck salinity, ammonia, nitrite, nitrate, kh, po4, mg, Ca 4/ Assuming all is working and everything is within NSW ranges go and buy the live rock. Transport it wet (wrapped in plastic is good enough for short journeys. Get it to the tank as soon as possible and arrange carefully. You can use acrylic pegs, milliput or cable ties to get it pinned in place. 5/ Top up the water with salt water mixed from zero TDS RO and your choice of salt. Premix the water for several hours with an airstone. 6/ Monitor the test results daily at first and then twice weekly or weekly as things settle down. Do a water changes often to keep ammonia and nitrate low during this time as this will preserve the life in the rocks. Once ammonia is staying low add a little (tiny amount) fish food daily to keep things alive and continue to monitor.
90W of T8 lighting over a 77gallon tank? I dont think that would be enough for Bacopa. It would grow long and stringy and the leaves on the lower part of the stem would be small or fall off. You could keep cutting the top off and replanting for a while but it would be high maintenance and eventually the plant would die. If you don't mind this routine and replacing the plant every 3-6months then it would be fine. Bacopa generally likes intense lighting so maybe double or triple what you currently have.
Reflectors effectiveness varies greatly depending on the tank design and that of the reflector. A closed lid tank with a white or silver interior often doesn't benefit from reflectors much at all but if you have an open top or black lined lid you'll get nearly double the light by installing them.
They're safe to leave on 24 hours, there should be some benefit but I don't know if you'd notice. You could run an airstone overnight to ensure that the CO2 doesn't build up - airstones are a good idea anyway as they help with circulation and oxygenation of the water.
This was a bit of a fad in the US last year. Initially there was the disgust felt by anyone who cares for animal welfare but I believe what actually closed them down was health and safety. Unless the fish are 'single use' there is a fairly large risk of cross contamination from one rancid foot to the next.