# PH changes with plants and lighting questions



## candymancan (Aug 16, 2013)

Two questions I have are... How often do you guys recommend I change the lights on my fixtures.. I have had my duel t5's on the 55g and 30g for about a year now.. I decided to get a 2nd duel t5 fixture for the 55g and got glass tops vs the old fashion single glass top it had for the old t8 fixture.. Reason was because with the single duel t5 in the middle when my fish swam to the front or back of the tank they were dark so I got 2 fixtures now for front and back.. and with the new t5 fixture I noticed the bulb are like night and day compared to the other fixture.. The 6700k bulb is white, and the old one looked white but now compared to it it looks yellowish... Obviously I need to get new bulbs for it..

And these are normal output lights. Having 4 of them over a 55g how high is this lighting roughly ? Im guessing more around the medium ish range ? and prior with only 1 fixture was on the low side right.. 


Now other question, my 27g hex my PH has always been in the 6.6-6.8 range and I had it heavily planted but the only fast grower was my water sprite.. I added a red tiger lotus in it about a month ago, and I noticed within less than a week of getting the tiger lotus my ph went to 7.4-7.6 and it isn't going down back to what it was.. Im assuming this tiger lotus just sucked every bit of natural co2 I had in the water.. (I don't dose co2 in air or liquid form) and can I reasonably assume this is also why my nitrates don't ever seen to go above 10-15ppm.. The tank is heavily stocked and usually after 1-2 weeks it would get high in nitrates... I noticed it just stays orange on the API test now.

Also what would happen if I put a T5 HO light into a T5 normal output fixture ?


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## corina savin (Jul 11, 2012)

It is recommended to change the bulbs every 9-12 months. I changed mine after 18 months and noticed a difference in plant's growth.

As for the pH, it is important when (what time in the day) you measure it (if you have plants) to get an idea how it changes over time (days, weeks). Generally, the best time is just before lights come on.
At that time, pH is at the lowest. Once the lights are on, plants start photosynthesis, CO2 is used up, pH start climbing, until all available CO2 is depleted. It may take few hours, hard to tell how long, it depends on many factors including the water's KH. When CO2 hits zero, pH is at the highest. If you remove a cup of tank's water, let it sit for 24 hours, it will outgas the CO2. Measure the pH in the cup (try to match the temperature with the tank since colder water can hold more CO2). The pH value in the cup after 24 hours is the highest for your tank.


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