Filtering freshwater systems

[MMaddox]

I don't know a lot about freshwater aquariums. There, I said it. I've been keeping marine systems for 15 years and am rarely confused by them anymore. However, our baby Mbu is in a 75 gallon tank temporarily until we move in two months. I'm currently running an emperor 280 power filter (I'm using a phosphate/silicate/nitrate absorbing media in the extra basket), and a wet dry filter rated for 125 gallons that I've upgraded the pump on (to ~500 gph) as well as almost doubled the bio-media in. However, the tank is still always very cloudy with what looks like a bacterial bloom and a greenwater bloom. I know the solutions to these problems is nutrient control, but we do weekly 75% water changes, and even that doesn't help for more than a day. I ordered a UV sterilizer which should clear the water, but doesn't address the underlying problem of excessive nutrients. I'm wondering how much more filtration I'm going to need...this wet dry kept a 90 gallon marine system with a much higher bio-load spotless. Grr, I don't like freshwater! >< Tips from people with big freshwater systems containing messy fish would be welcome!

[edmlfc1]

How long has the tank been cycled? What are your test results?

[Dadof4]

What is your substrate? And why do you think this is an bacteria bloom? I think your filter system is more that adequate but I would suggest placing filter floss in the emperor and lower you lighting. This has worked for me in the past. That could just be suspended organic material in the water that is too small for the current mechanical filtration to remove.

[Nick]

A wet/dry can produce a LOT of nutrients in freshwater, with no skimmer to remove them...

[Corvus]

In freshwater tanks plants are a most valuable competition to all types of unwanted photosynthetic life, be it green cloudiness by bacteria or protozoans, or simple algae.

I'd take the phosphate, nitrate, silicate adsorbers out, establish a plantable substrate and plant it according to the illumination available. The sterilizer will also only treat the symptom, plants will help with both once established: take up the nutrients and fight algae biochemically.

Plants are somewhat the "life rock" in freshwater. A planted freshwater tank is generally very stable.

[MMaddox]

The tank is already planted - maybe I need more? A sterilizer completely cleared the water, and the params are fine... *confused*

Substrate is flourite, with silica sand on top. Before everyone says "it's the silica sand!" it's not - silica sand barely dissolves in water, and my silicates don't register on a test.

The tank is about 6 months old, filtered by a penguin 280 (with seachem's phosphate absorber in the basket) and a wet/dry with almost double the amount of media it came with with (lots of extra bags of ceramic rings in addition to the full container of bioballs) ~450gph flow rate, and now a gamma UV sterilizer on the wet/dry return.

[Agnate]

If you had a greenwater bloom, it was likely just a combination of light and excess nutrients. If the UV sterilizer cleared things up, then you're good to go.

What kinds of lights are you using, and how much plant do you have in there? It might be worthwhile to add in CO2 if you only have a small Mbu in there. Until he gets bigger, he won't be providing nearly enough CO2 to allow your plants to suck up those nutrients.

I'm no plant expert though, so you can take my advice with a grain of salt.