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Hi. I've got a well-established 55-gallon tank with an assortment of about 19 fish, including one buttokoferi (tilapia) that's gotten 3x bigger than anything else in the tank yet everyone pretty much gets along -- surprisingly. Water chemistry is really quite good except that I battle mildly high levels of nitrate, and even 40% water changes don't bring it down.

I've been told now that the type of gravel I have in there, a fine, black ground up lava, is too dense and as such it too hard to clean. Over time, this has resulted in higher nitrate levels, and I also think it's contributing to a pH that creeps downward from time to time, i.e., from 7.5 to as low as about 5.5.

Does that explanation make sense?

If so...my question is what is the best, most effective way of doing a gravel exchange in an established tank when I don't have a spare tank? I'm thinking of exchanging the lava gravel for something neutral in color, larger and easier to vacuum). Is a major cycling unavoidable?

I'd like to keep as much of the existing water as possible -- does this plan sound feasible:

* Leave all filtration intact but turn off
* Siphon most of the water to a (new and well-rinsed) 35 gallon plastic trash can.
* Stick the fish in the trash can
* Remove the old gravel
* Wash and place the new gravel
* Siphon back in the water from the trash can
* Stick the fish back in
* Replace the plants
* Add a bunch of Cycle
* Watch the chemistry closely for a week or two.

Any input is appreciated.

I switched out the ugly purple gravel that my used tank came with for sand...your plan of attack is pretty good I'd just reccomend the following..

~Use rubbermaid (or similar) tote containers (more surface area than a trash can). Get solid color (opaque) containers with lids. No light means less stress for the fish.

~Remove and run the filters on the temp tanks, that will give you more than the hour you would have if you just left them turned off.

~Make sure the new substrate is well rinsed prior to placement in the tank .

~Save some of your old substrate and place in nylons in front of the filter or shallow containers (these can be hidden behind decor). This will help preven the mini cycle from occuring.

~Only use the prescribed ammount of cycle, while you cant technically overdose (okay you could if you dumped 5 bottles in) excess cycle seems to cause a high spike in nitrItes that doesn't go down for weeks.

^_^[hr width='40%']"I'm alright, I'm alright
It only hurts when I breathe"

FreshFishy

I fully agree with all Babelfish stated.
You did not mention a heater or did I miss something. Certainly run that in the temp containers as well.

Another tip start early in the morning as it could take all day.

Have the new base washed and rewashed to make sure it is perfectly clean. I would also add some very hot water to the base before you put it into the new tank this will then take less time to reheat as the way you are doing it you will have no spare time at all. As soon as the water goes in you intend to add the fish am I correct.

Also if it is planted and aquacaped do all that with the minium amount of water.

Have plenty of time dont rush & plan it all out and there will be no problems.

Keith

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