I bought a Fluval Edge (6gal with a "standard" fluval filter rated at 20gals) about six months ago. To do the initial cycle, I added about 10lbs of rinsed sand (just under 2"), a couple small decorations and about 8 (very) small feeder goldfish. After about two-three months, the tanks' nitrogen cycle was very stable, and the goldfish retired to the rain barrel outside to live a comfortable life eating mosquito larvae.
I then decided to put in a gourami and three cory cats, with the expectation that if the cories or gourami ever outgrew the tank, I'd move them to another. At the time, the gourami was about 2" and each of the cories were about 3/4", so I felt safe that I was well under the "one inch of fish per gallon" rule.
I vacuumed (as well as one could) the sand weekly and did about 1/3 water changes (it is VERY hard to move a vac around this tank). Then, out of nowhere, I wake up one morning, one of the cories is dead and the gourami has little brown lesions all over his head.
I check the tank: no nitrites/nitrates, a pH of less than 6.2 (the lowest my kit will read - the kit reads in shades of yellow, green and blue, but this was a paler yellow than the lowest reading), and ammonia at greater than 8.0ppm (higher than my kit will read - my kit reads in shades of yellow and green and this was navy blue). I freak out.
I stirred the sand (to get what waste I could floating in the water) and do a 50-60% water change. I go to rinse out the media in the tank water and notice that it's gone from slightly brown (as it had been the past 3+months) to pink and the sponge has gone from slightly brown to blood red. Yes, I've changed my sponge and media once every two months, per package instructions, this was in the middle of the second sponge/media combo. I tossed the sponge and media - they aren't supposed to be that color!
I get everything back into the filter, add water (I don't need a dechlorinator because my water is filtered and has perfect readings across the board) and add Neutral Regulator to put back some of the calcium and magnesium that my water filter takes out. I drop in about 3/4tbsp aquarium salt to help the chemical burns on the gourami and the obviously suffering cories. After about two hours, the gourami has calmed down and the cories are back to doing cory things.
The next morning, I wake up and I walk past my tank and catch a whiff of what I thought was windex. I check the readings again, and again we're above 8ppm on amonia, but today the pH is ok. I do a 30% water change and get the ammonia back down to ~4ppm. This continues day after day with wildly fluctuating ammonia and pH readings. Ammonia is always too high, pH is almost always too low. I'm heading to the lfs every two or three days for new chemicals, new bacteria, you-name-it.
Finally, I decide that, although I really like the guy at the lfs, I start consulting google because daily water changes CAN'T be good. I start reading about buffering capacity and look at the areas of my test strips I've never really paid much attention to, and realize that, well, my tank has no buffering capacity, despite adding Neutral Regulator at every change. I order (because the lfs doesn't cary) crushed coral from Amazon. I rinse everything out, mix it into the sand and we have no more wild pH swings. I do some more research on the ammonia problem and I run across "Zeolite" and "AmmoLock". I order both, figuring one will do if the other doesn't. Boy, was I wrong.
The Zeolite completely ignores the ammonia in the water, in stead dropping overall Alkalinity (apparently it prefers calcium to ammonia) and AmmoLock's effects never last more than a few hours. No nitrites. No nitrates. Ever.
Fish are only getting food every other day (the gourami has now taken to striking at the top of the tank when I walk by).
After more reading, I came to the conclusion that sand may not be the best freshwater substrate. I siphoned out the tank water, removed the sand, put a mix of crushed coral and gravel (again, just under 2"), removed all decorations (except for one hidey hole for the cories). This was about 4 weeks ago and I'm still having daily ammonia spikes and have never seen nitrates or nitrites in the tank since the goldfish moved out. As well, I've never seen the "brown fog" that was present when the goldfish were there (bacterial colonies in-tank).
I've been doing daily water changes for almost 10 weeks now.
So...here are a couple bits of info about how I'm trying to care for this tank:
1: Inhabitants: one opalescent gourami (approx 2") & two corydora cats (<1")
2: Ammonia: between 4 & 8ppm depending on whether a water change has just been done. Nitrites/Nitrates: 0. Chlorine: 0. Total Hardness: between 250 and 425 (it's hard to tell with my strips). Total Alkalinity (buffering capacity): about 160ppm. pH: stable-ish at about 7.4.
3: 6gal tank. Tank has been set up for a total of 6 months. Currently attempting second cycle due to substrate change.
4: Filtration: 20gal Fluval Edge (came with tank). Recently added additional 6.6gal Marineland in-tank to assist.
5: Daily water changes of between 20 and 50% depending on that day's ammonia reading. Gravel/crushed coral substrate is thoroughly agitated every time.
8: Current fish have been in tank almost 3months.
9: Fish food: NutraMax flake & Hikari sinking algae wafers (small).
10: Chemicals/Bacteria: Neutral Regulator at water changes (the coral seems to make the water a tiny bit more basic than I'm comfortable with for the cories), NiteOut & Stabilizer (nitrogenous bacteria) and Prime. All chems & bacteria added at water change time in amounts recommended on container for amount of water changed or aquarium size.
I know I'm doing too much: my son has a 2L tank in his room that we barely have to touch, except to replace evaporated water every week. The 55 gal in the living room is also perfect. I've even gone so far as to doing water changes from the 55 into the 6gal to try to get things moving. Is my Fluval Edge just haunted?
I then decided to put in a gourami and three cory cats, with the expectation that if the cories or gourami ever outgrew the tank, I'd move them to another. At the time, the gourami was about 2" and each of the cories were about 3/4", so I felt safe that I was well under the "one inch of fish per gallon" rule.
I vacuumed (as well as one could) the sand weekly and did about 1/3 water changes (it is VERY hard to move a vac around this tank). Then, out of nowhere, I wake up one morning, one of the cories is dead and the gourami has little brown lesions all over his head.
I check the tank: no nitrites/nitrates, a pH of less than 6.2 (the lowest my kit will read - the kit reads in shades of yellow, green and blue, but this was a paler yellow than the lowest reading), and ammonia at greater than 8.0ppm (higher than my kit will read - my kit reads in shades of yellow and green and this was navy blue). I freak out.
I stirred the sand (to get what waste I could floating in the water) and do a 50-60% water change. I go to rinse out the media in the tank water and notice that it's gone from slightly brown (as it had been the past 3+months) to pink and the sponge has gone from slightly brown to blood red. Yes, I've changed my sponge and media once every two months, per package instructions, this was in the middle of the second sponge/media combo. I tossed the sponge and media - they aren't supposed to be that color!
I get everything back into the filter, add water (I don't need a dechlorinator because my water is filtered and has perfect readings across the board) and add Neutral Regulator to put back some of the calcium and magnesium that my water filter takes out. I drop in about 3/4tbsp aquarium salt to help the chemical burns on the gourami and the obviously suffering cories. After about two hours, the gourami has calmed down and the cories are back to doing cory things.
The next morning, I wake up and I walk past my tank and catch a whiff of what I thought was windex. I check the readings again, and again we're above 8ppm on amonia, but today the pH is ok. I do a 30% water change and get the ammonia back down to ~4ppm. This continues day after day with wildly fluctuating ammonia and pH readings. Ammonia is always too high, pH is almost always too low. I'm heading to the lfs every two or three days for new chemicals, new bacteria, you-name-it.
Finally, I decide that, although I really like the guy at the lfs, I start consulting google because daily water changes CAN'T be good. I start reading about buffering capacity and look at the areas of my test strips I've never really paid much attention to, and realize that, well, my tank has no buffering capacity, despite adding Neutral Regulator at every change. I order (because the lfs doesn't cary) crushed coral from Amazon. I rinse everything out, mix it into the sand and we have no more wild pH swings. I do some more research on the ammonia problem and I run across "Zeolite" and "AmmoLock". I order both, figuring one will do if the other doesn't. Boy, was I wrong.
The Zeolite completely ignores the ammonia in the water, in stead dropping overall Alkalinity (apparently it prefers calcium to ammonia) and AmmoLock's effects never last more than a few hours. No nitrites. No nitrates. Ever.
Fish are only getting food every other day (the gourami has now taken to striking at the top of the tank when I walk by).
After more reading, I came to the conclusion that sand may not be the best freshwater substrate. I siphoned out the tank water, removed the sand, put a mix of crushed coral and gravel (again, just under 2"), removed all decorations (except for one hidey hole for the cories). This was about 4 weeks ago and I'm still having daily ammonia spikes and have never seen nitrates or nitrites in the tank since the goldfish moved out. As well, I've never seen the "brown fog" that was present when the goldfish were there (bacterial colonies in-tank).
I've been doing daily water changes for almost 10 weeks now.
So...here are a couple bits of info about how I'm trying to care for this tank:
1: Inhabitants: one opalescent gourami (approx 2") & two corydora cats (<1")
2: Ammonia: between 4 & 8ppm depending on whether a water change has just been done. Nitrites/Nitrates: 0. Chlorine: 0. Total Hardness: between 250 and 425 (it's hard to tell with my strips). Total Alkalinity (buffering capacity): about 160ppm. pH: stable-ish at about 7.4.
3: 6gal tank. Tank has been set up for a total of 6 months. Currently attempting second cycle due to substrate change.
4: Filtration: 20gal Fluval Edge (came with tank). Recently added additional 6.6gal Marineland in-tank to assist.
5: Daily water changes of between 20 and 50% depending on that day's ammonia reading. Gravel/crushed coral substrate is thoroughly agitated every time.
8: Current fish have been in tank almost 3months.
9: Fish food: NutraMax flake & Hikari sinking algae wafers (small).
10: Chemicals/Bacteria: Neutral Regulator at water changes (the coral seems to make the water a tiny bit more basic than I'm comfortable with for the cories), NiteOut & Stabilizer (nitrogenous bacteria) and Prime. All chems & bacteria added at water change time in amounts recommended on container for amount of water changed or aquarium size.
I know I'm doing too much: my son has a 2L tank in his room that we barely have to touch, except to replace evaporated water every week. The 55 gal in the living room is also perfect. I've even gone so far as to doing water changes from the 55 into the 6gal to try to get things moving. Is my Fluval Edge just haunted?