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Our Tropical Fish Tank

Updated on March 3, 2011

Setting Up

This is a blog about my first ever tropical fish tank - hopefully it will be informative and interesting...

The bog wood has been soaking in a bucket for 2 weeks. The missing cabinet part arrived yesterday so that was put together - I'm only a little concerned about having something that weighs in excess of 130Kg on something I built myself! Spent a good while trimming the background to the right size. We decided to wedge it under the plastic top of the tank so that it can sit completely flat. Didn’t have to worry too much about cutting it accurately as the edging of the tank and the sealant will cover any edges. Not being any more organised, I cellotaped it down, again hiding the tape behind areas that won’t be seen.

I have 2 bags of kids play sand from Argos (bargain £3 each).  This was chosen because I am planning on having fish that may want to burrow in the substrate and find food in it.  Sharp gravel tends to damage the barbels on the fish that burrow in this way and after looking online, it seems play sand is perfectly fine (and a lot cheaper than aquarium sand).  The sand will be washed thoroughly before placing in the tank

I should mention it's a 125l tank. Aiming for a 30 day cycle before introducing the fish.


Filling the Tank


The tank got filled on Friday. It took at least 12 buckets of water and a measuring jug to tip it in. Didn’t bother pouring it on to a saucer on top of the substrate, as it's easy to move the sand around with the water on top, so long as you don’t mind getting wet. Plus the miniature sand dunes look quite natural (imitating the river and lake beds where our fish would be at home. Wonder if some will gravitate to the moving water and others prefer to be further from the filter. Mind you, probably all so over captive bred they'll have forgotten what it could be like).

Used the flattened cardboard box the tank came in and a towel on the floor to catch the worst of the spilling water when filling the tank - it was quite a mess pouring so much water in from the bucket on the floor.

Added the dechlorinator (Aqua Plus) once the tank was full of tap water. Filter and heater are now in the tank and working. Had to slant the heater, which doesn’t look so good but whatever will make the fish happier, they get. Temperature was 27C this morning - it's rising slowly and needs to be 29C.

Broke the bottom of our decorative broken urn (more authentic?). It'll be dug into the substrate so I don’t think it'll look too bad, especially once it's been in the tank a while and looks more natural.

Dawned on me this morning that we will need an automated switch for the lights, if only for when we're on holiday.

Have taken some photos, will learn how to post them this evening!

Cycling the tank - techie stuff


OK, I hope everyone remembers their chemistry/biology from school as I thought I should write a bit about the science behind the tank cycling..

Fish produce waste products called Ammonia and Nitrite (not to be mistaken for Nitrate), which are both very toxic to tropical fish.  In order to remove these chemicals from the tank we need to rely on the Nitrogen Cycle.  In a nutshell, this is when Ammonia is converted to Nitrite, which in turn is converted to Nitrate which is then taken up by plants as fertiliser.  In order to get from Ammonia to Nitrite, and then from Nitrite to Nitrate we need the help of two different types of Nitrifying bacteria. Wow, my Environmental Science degree finally comes in useful!

So, to recap we have a process like this:

Ammonia - (Nitrifying bacteria A - let's call them Bob) - Nitrite - (Nitrifying bacteria B - let's call them Janet) - Nitrate

It should be noted that Nitrate is also slightly toxic to these fish but you can have quite high levels before they start to feel the effects.  When the Nitrate is built up to a high level, a water change is undertaken and new (dechlorinated) tap water is added. It is important that this tap water is dechlorinated as Chlorine kills bacteria and will destroy all the hard work.

These nitrifying bacteria exist at trace levels in tap water and all around us but the quantities are very small, so if a whole tank of fish is added, there would not be enough bacteria to cope with the high levels of Ammonia and Nitrite and the fish would most likely all die.  For this reason we are going to "cycle" the tank so that the levels of bacteria can build up to a level that can handle the addition of the fish. 

The bacteria will live predominantly in the filter (this is the primary purpose of the filter) and need a source of food to build themselves up and prevent them from starving.  For this reason Ammonia (about 4-5ppm) is added to the tank to give the Bobs something to feed on and increase their numbers.  The level of Ammonia in the tank will be monitored, and when it starts falling it can be deduced that the Bobs are doing their job.  Once the levels have fallen from 4ppm to 0ppm in 12 hours, we can assume that we have enough Bobs to handle the addition of the fish, we now need to build up the levels of Janets.  We don't need to add any Nitrite as the Bobs are already creating it for us.  Hopefully, by the time the Ammonia is falling to 0ppm in 12 hours, the Janets will have started to increase in numbers.  There is quite a bit of lag here as the Janets are a little harder to encourage to grow so at this point there will likely be a huge amount of Nitrite in the tank (known as a Nitrite spike) so the water will be the most toxic at this stage.  There is no safe level of Nitrite so we need to wait for this to reduce to zero and stay there.  All the time, Ammonia will be added to keep the Bobs allive.

It is also possible to do this cycle with fish present. In order to do this, obviously no Ammonia would be added and the water will need daily changing to manually remove the Ammonia and Nitrite until the bacteria have built up enough numbers. Hardy fish are needed to do this, and even then there is a possiblilty the fish will be killed so we decided not to go down this road.

The first lot of Ammonia was added on Friday but so far had not reduced.  I will keep monitoring the levels most days from now on...

Phew, that's it I think!  Now, any questions??

Cycling - Evidence of bacteria

 After a week or so, we started to see the Ammonia levels decreasing and the nitrite levels increasing, which casued a great deal of excitement as this indicates the arrival of some bacteria.

Unfortunately, we have subsequently been having some problems with the ammonia levels. They dropped to 0.25 but I now think this was a misreading and actually 0 as the Bobs have been dying off. I've now twice re-dosed the tank with ammonia to see if the bacteria will start growing again. The reading was at 0.25 for about 4-5 days, and Bobs can only last a few days without ammonia.

I took the rocks out last night to see if they were affecting pH levels. Glad to say that they passed the white vinegar and nitrate tests (a few drops of vinegar to see if the rock fizzes, and drops of a nitrite water tester to check the rock is inert). pH is up to about 8.3. Now it's a waiting game for the Bobs and Janets to get going properly.

This is the empty tank in place
This is the empty tank in place
The tank is full of water, sand and ready to go.
The tank is full of water, sand and ready to go.
First Nitrite readings.
First Nitrite readings.

Janets start to work but still no Bobs.

The latest read outs from the tank are:

Ammonia: 4ppm
Nitrite: 0ppm (ie we killed off all the Bobs we'd bred)
Nitrate: >40ppm (some Janets, but they may not last unless the nitrite goes up very soon)
Ph: 8.3

This is almost exactly where we started but a higher pH and more nitrate.  This indicates that there is now bacteria processing the nitrite to nitrate but they have no used up all the nitrite in the water and I fully expect them to start dying off because the Ammonia is no longer being processed.

I have found the following forum to be really helpful when setting up the tank, there is a lot of info for new tank owners and people on there are always ready to help


3/3/2011 - No Bacs

 Well, we are a week on and there has been no movement in the Ammonia levels.  I can only assume all the bacteria are dead and this past month has been a waste!  Therefore we decided to do a 50% water change two nights ago.  The idea is that it will give a fresh influx of new bateria, give us some practice for when we have to do this with fish and, well, just to make me feel like I am doing something!

The pump is like a manual syphon so to get it started I moved it quickly up and down to get the water flowing, after this the water continued to flow thanks to the forces of gravity and it continued to suck up the water.  We syphoned it into a washing up bowl and the whole process was suprisingly easy.  It was more time consuming getting the new water back in as it had to be treated to remove Chlorine and to try and get it somewhere near the 29 degrees of our tank water. 

In any case, it was all done in just over an hour and I now feel like it's a fresh start.  I took some readings last night, and it might have just been my imagination but I thougt I saw the dark green Ammonia test water (green signifies Ammonia presence) look a bit lighter....


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