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Custom Filter!

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Fish Fanatic
Apr 11, 2020
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So since my last post about the problems I had with my internal filter. I was undecided on what filter to go for next. I really liked the idea of how the Fluval flex tanks had the filter built into the back of the tank. Its discrete, allows you to hide the heater and has plenty of space for sponges and media. But I didn’t want to change my tank as I really liked the one that I have. So I went ahead and built my own filter, using the pump and nozzle from the fluval flex tank and some pre cut plastic acrylic I ordered online. The filter has two compartments. The first compartment houses the sponges, filter floss and biomedia. The water flows into the compartment low level just above the substrates, and passes through the sponges first, then the filter floss, then the media. To which the water then enters the second compartment at high level. The water will then flow past the the heater and into the pump, then finally back out again into the main area of the tank. It has worked out quite well and I am very pleased. Please let me know what you all think.

Furthermore I have had a bit of spike with my Ammonia levels…. (I will carry on with a follow up post)


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Following on…. When I first emptied the tank, I moved the filter, heater and the water into a second aquarium for the fish to love temporarily. The sand and the plants and aquarium water went into a bucket. They was all there for approx 72hrs. While i built the custom filter into my tank. After the 72 hours I added the sand, the plants and the water out of the bucket into the aquarium along with some fresh treated water. and i turned the filter on. I add in some fluval cycle biological enhancer and let the tank run for 24hrs with out the fish. I then drained out some of the water to allow me to move the fish back into the tank along with the water they was currently in, in the temporary smaller tank. I then added some more fluval cycle enhancer. Then yesterday (the third day of the tank running) I added the last dose of fluval cycle biological enhancer. I feel like I have done this correctly to try and keep the majority of the good bacteria that was existing but also I know I will have lost all the bacteria on the tank from it being empty and dry whilst i was making the filter. It has now been 48hrs that the fish have been in the tank and all seems well except I have had a spike in ammonia and also my nitrate is a bit high. I am going to do another water change now, and see if it makes a difference. But any tips or ideas to help will be appreciated. Thanks
There doesn’t seem to be much change after the water change I did yesterday. Please see attached photos, which I have marked up. (after taking the picture of the Ammonia Tests, I was unsure which was the before and after)

I am going to do another water change later on today when I get home. Anyone got any advice ?


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Looks like 0 ammonia, from what I see; and nitrAtes aren't too high, either.

Are you shaking the 2nd nitrAte test kit solution like mad before adding to the test tube? If not, you will get erroneous results.
Yeah, I was unsure if its 0 or 0.25ppm. to me it looks like it has a slight look of the green. Yeah i'm certain I am shaking the bottle like mad
Yeah, I was unsure if its 0 or 0.25ppm. to me it looks like it has a slight look of the green. Yeah i'm certain I am shaking the bottle like mad
I think you're in good shape...continue to monitor those params, and perform weekly WCs...
What light are you reading the ammonia test under? Daylight, but not direct sunlight is best, and incandescent and halogen bulbs are also OK but fluorescent lights, both tubes and compact fluorescent bulbs, can make the colour look greener than it really is.
I don't know if LED lights have any effect. I need to do some testing.
Im reading it under a fluorescent bulb. So maybe thats why I’m seeing a greenish colour. I will do another water test tomorrow and try and read it in the daylight. Hopefully it shows it to be 0ppm!

Thanks for the input 👍🏻😀

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