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GwenInNM 08-14-2011 06:18 PM

Guidance with changing gravel

Okay, today got a free tank with some fish from a friend. It's about a 30 gallon. We did a 80 percent water change to move the tank over to my house. I do see lots of debris in the gravel and she said it used to have an underground gravel filter, so it has this "plastic lining" on the bottom. I was shocked today when I saw the nitrate reading at 80ppm (after I put clean water back in the tank)!!. I knew my neighbor wasn't that diligent about cleaning, but wow. None of my tanks would ever get even close to that number. There is a fish in the tank over 10 years old, so they are used to living in this type of tank, but I'm planning on taking out the gravel (as much as I can) and adding my own gravel that I have.

My question is, does the underground filter thingy have to come out? Perhaps there is lots of "junk" down under that, which is causing such high nitrates. She has just a few plants, which also have some stringy algae on them, but not enough plants to do much.

This will be a project for me soon, and I'd like to know what is the best way to proceed - take out the underground gravel thing?? There is a bio-wheel filter on the tank, so any parts left from the underground gravel may be contributing to the problem. I'd like to leave something, to prevent a min-cycle - perhaps I should put some gravel in a mesh bag and float for some time? Thanks for suggestions.


AbbeysDad 08-14-2011 10:50 PM

You should completely tear down the tank. An under gravel filter (UGF) works just fine if the gravel is routinely cleaned. Think of it like any other filter media - the 'crud' needs to be removed periodically, This is easily done with a gravel siphon...

However, in this case, I'm suggesting you tear it all down, clean and set it back up. So yes, that means removing the UGF and thoroughly cleaning the gravel. You can decide whether or not to continue to use the UGF. I use one in my 10g fry tank and I'm happy with it, but I gravel siphon weekly to keep the media (gravel) clean.

footnote: the only problem with UGF's is many folks just don't clean the gravel and in time, it becomes loaded with detris crud and as you have discovered, can become a "nitrate factory" - this is not an issue with periodic gravel (siphon) cleaning :-)

Byron 08-15-2011 12:04 PM

I agree with AbbeysDad. Do not put fish in this tank because the high nitrate will damage them internally. Except those that she had (if you got them too) as they are used to this mess.

If you do re-use the gravel, wash it under very hot tap water to kill all bacteria. The heterotrophic (deniytrifying type) will survive drying out but not chlorine.


twocents 08-15-2011 12:44 PM

Also, when you remove the fish from this tank, acclimate them to wherever they are moved to. Since the levels are over the top, I would do it very slowly.

willow 08-15-2011 02:18 PM

i'm with the others,gut it completly.
i've just done this on my 4ft tank,it was hard work,but so worth it.

GwenInNM 08-15-2011 04:59 PM

I agree, I've decided that is what I have to do, even if these poor fish are used to living like this for years now. I will not keep the gravel, I have gravel I like more. I'll keep enough to put in mesh bag so there is some "good" bacteria, as I don't want to have the tank go into a cycle. Of course I will also keep the filter media that is in the filter. I have no intention of adding fish to this tank at this point, if you thought I was thinking about that :) I just was wondering how that undergravel filter thing may be contributing, and I see that there is probably tons of junk stuck under it. There has not been an underground filter for years. The part is just still in the tank.

I really don't want the fish (Whiteclouds) that need cooler water, because that does limit me, plus the other fish in there will need a heater when winter comes. I'll check and make sure my neighbor won't be hurt if I rehome them for her. Thanks all for the help!


willow 08-16-2011 01:08 PM

good luck,i hope it all goes ok for you. :)

GwenInNM 08-16-2011 07:17 PM

Yes, I did it last night and all went great. Fish are fine, and I'm sure they are happier now that the nitrate reading is 5ppm. I did not rinse out the filter, and I put the log with java fern back in and a crypt that looks pretty sorry, but with fertilizer I'm hoping will do better. I tossed the gravel she had, and added gravel that I had held on to, after I switched my 2 tanks to playsand. It wasn't so bad after all, doing a complete tear down - but the tank is not that big either. I'm leaving these fish alone for awhile, no more major upheveals, but I one day want to re-home the White Clouds.


willow 08-17-2011 07:10 AM

glad it all went well. :-D

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