Planted Cycle - Away for 5 Weeks?


New Member
Nov 24, 2019
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Hi all, I have a question about cycling my planted tank. I am a college student, and was planning on cycling the tank with some media from a friend, but I realized that that aquarium was saltwater. Will the media from a SW tank help to cycle a FW tank?

Also, my plan for the time frame was to get the tank planted with everything except the fish (heater, light, filter, PFS substrate with liquid fert, etc) the week after Thanksgiving. I will be around for a week after that, then I'm headed home for break for about 5 weeks. I was planning on dosing with ammonia or some kind of bacteria starter as soon as I get the tank set up, and monitoring for those two weeks that I'm still at school, then letting it do its thing until I get back. I will be able to leave everything plugged in, but is this a recipe for disaster? I was thinking it would be a good way to let the plants get established and the ammonia cycle happen with the help of the plants, but I don't want to have spent all that time and money for all the plants to melt away or something like that.



Fish Guru
Feb 25, 2009
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Welcome to TFF.

To get the question of saltwater cycling out of the way quickly...I doubt this will work. I am going from memory, but I believe Dr. Tim Hovanec and his team discovered that the nitrifying bacteria for freshwater are different from those for marine (salt water). Anyway, it isn't necessary as I will explain, and one should never use media/substrate from someone else's aquarium, you can easily introduce pathogens.

To the issue, with live plants there is no need to "cycle" an aquarium. Using ammonia with plants present can work, but remember that ammonia is toxic to all life forms (except the bacteria that consume it!) and it is easy to kill the plants. Just plant the tank and get it running. If the plants show signs of growth, it is safe to introduce fish. Fast-growing plants--and here floating are the best--will easily take up all the ammonia a few fish can produce--or a lot of fish if the tank is established and the plants are growing well.

I have set up tanks for more than 30 years, always using live plants (and always floaters included) and never once "cycling." Nothing could be simpler.

Since you are going to be away for a couple weeks, I would not introduce fish. But get the plants going, have the tank light on a timer (constant light will harm fish and plants, and cause algae problems), and all should be well. Fertilize the plants as there will be no fish producing natural organics. Seachem's Flourish Comprehensive Supplement for the Planted Aquarium is a good complete liquid, and another is Brightwell Aquatics' FlorinMulti.

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